ILLINOIS 
STATE  GEOLOGICAL  SURVEY. 


BULLETIN  No.   11. 


Physical  Features  of  the 
Des  Plaines  Valley 


BY 


James  Walter  Goldthwait 


Urbana 

University  of  Illinois 

1909 


SPRINGFIELD,  ILL.. 

Illinois  State  Journal  Co.,  State  Printers 

1909 


1 


STATE  GEOLOGICAL  COMMISSION. 


Governor  C.  S.  Deneen^  Chairman, 
Professor  T.  Q.  Ciiamberlin,  Vice-Chairman. 
President  Edmund  J.  James,  Secretary. 


H.  Foster  Bain,  Director. 

E.  D.  Salisbury,  Consulting  Geologist,  in  charge  of  the  preparation 
of  Educational  Bulletins. 


.%' 


TABLE  OF  CONTENTS. 


Page. 

List  of  illustrations yii 

Letter  of  transmittal ix 

Ctiapter  I.    Geography  and  history  of  the  Des  Plaines  river 1 

Introduction  1 

The  Des  Plaines  basin 3 

History  of  the  Chicago  portage  and  the  canals <> 

Chapter  IL    The  structure  of  the  bed  rock 10 

Deposition  of  Paleozoic  sediments 10 

Nature  and  age  of  the  rocks 10 

The  Cambrian  period  11 

The  Ordovician  period 12 

The  Silurian  period 14 

The  Devonian  period 17 

The  close  of  sedimentation 19 

Warping,  jointing,  and  faulting  of  the  rocks 19 

P'olds 19 

Joints 20 

Faults 21 

Chapter  IIL    The  concealed  surface  of  the  bed  rock 23 

Significance  of  the  buried  topography 23 

Pre-glacial  denudation 24 

Deductions  from  the  driftless  area 24 

The  pre-glacial  topography 24 

The  development  of  underground  drainage 25 

Glaciation 26 

The  glacial  period  26 

The  smootiiing  and  striating  of  the  rock  surface 29 

The  burial  of  the  rock  surface  with  drift 30 

The  buried  topography 31 

Chapter  IV.    The  glacial  and  interglacial  deposits ;.  33 

The  distribution  and  surface  form  of  the  drift • 33 

Thickness  of  the  drift 34 

Complexity  of  the  drift 35 

The  two  kinds  of  drift 35 

The  ice-laid  drift  or  till 36 

The  stratified  drift 38 

The  Joliet  conglomerate 42 

Chapter  V.    Physiographic  history  of  the  lower  Des  Plaines  river 46 

General  description 46 

Deposition  of  the  early  Wisconsin  drift 47 

The  early  Wisconsin  moraines 47 

The  lake  in  the  Morris  basin 48 

Deposition  of  the  late  Wisconsin  drift 48 

The  Minooka  till  ridge 48 

The  Valparaiso  morainic  system  and  its  outwash 49 

.    Excavation  by  the  outlet  of  Lake  Chicago S2 

Glenwood  stage.    Excavation  of  a  trench  in  the  valley  train 52 

Calumet  stage.    The  Lockport  sill 54 

Toleston  and  later  stages.    Abandonment  of  the  outlet  and  substitution  of  the  Des 

Plaines  river 55 

Erosion  by  tributaries 57 

Fraction  run 57 

Long  run  and  other  tributaries  above  the  sill 59 

Spring  creek  and  Hickory  creek 59 

Sugar  creek 60 

Reed's  woods  ravine 60 

Alluvial  fans  and  cones 64 


VI 

Table  of  contents — Concluded. 

Page. 

Chapter  VI.    Physiographic  history  of  the  upper  Des  Plaines  river 66 

Deposition  of  the  till  ridges 66 

Lake  Clucajjo 67 

(jleiiwood  stage '. 67 

The  Oak  Park  spit U7 

Siioreline  l)et\veen  May  wood  and  Mt.  Forest 73 

Calumet  stage "ii 

Emergence  of  the  floor  of  Des  Plaines  Ijay 74 

The  Calumet  shoreline 75 

Toleston  stage 7h 

Extension  of  tlie  Des  Plaines  river  near  Riverside 78 

Renewed  trenching  of  the  valley 79 

The  Toleston  shoreline  .' 79 

Subsequent  changes  leading  to  formation  of  Lake  Michigan 81 

Excavation  of  the  valley  81 

Development  of  tributaries 86 

Chapter  VII.    Kloods  on  the  Des  Plaines  river 88 

The  upper  river 88 

Tlie  lower  river ." !•! 

Appendix.    Suggestions  for  field  trips 94 


VII 


LIST  OF  ILLUSTRATIONS. 


Plates. 

Page. 

1.  Fossils  from  the  Niagara  formation 16 

2.  (a)   Lock  on  the  Illinois-Michigan  canal  above  Joliet 22 

(b)   Fault  in  the  wall  of  the  Sugar  creek  gorge  22 

3.  Pebbles  from  the  drift 36 

4.  (a)   Stratified  drift  at  Overholser's  pit,  Joliet 40 

(b)   Exposure  of  Joliet  conglomerate  near  Spring  creek 40 

5.  (a)   Outwash  terrace  on  Spring  creek 42 

(b)   Fraction  run  above  Dellwood  park 42 

6.  Map  of  the  gorge  of  Sugar  creek 60 

7.  Map  of  the  ravine  in  Reed's  woods 62 

8.  (a)   Young  gully  near  Reed's  woods ,. 76 

(b)  Calumet  beach  ridge  at  Summit 76 

9.  Effects  of  a  recent  flood  on  Hickory  creek 92 

Figures. 

1.  Map  of  the  Des  Plaines  basin 2 

2.  Section  through  the  rock  in  a  deep  well  at  Lockport 10 

3.  Nortli  America  in  Potsdam  and  in  Trenton  time 13 

4.  North  America  in  Niagara  and  in  later  Devonian  time i 1,5 

5.  Map  of  the  North  American  ice  sheet 26 

C.           Map  of  the  moraines  in  Illinois „ 28 

7.  Sections  of  residual  soil  and  of  drift 29 

8.  Block  diagram— The  ice  sheet  and  the  west  ridge  of  the  Valparaiso    morainic  sys- 

tem   40 

9.  Block  diagram— The  ice  sheet  and  the  Valparaiso  moraine 41 

10.  Map  of  the  lower  Des  Plaines  river 47 

11.  Maps  showing  two  stages  of  Lakes  Cliicago  and  Maumee 5.3 

12.  Diagram  to  illustrate  'stoping"  in  tlie  Chicago  outlet ."iS 

13.  Block  diagram— Effect  of  recession  of  falls  on  tril  lutaries 58 

14.  Block  diagram— A  crooked  gully 62 

15.  Block  diagram— A  meandering  gully 63 

16.  Map  of  part  of  Lake  Chicago.    Glenwood  stage 68 

17.  Map  of  the  district  about  Oak  Park  and  May  wood 70 

18.  Map  of  part  of  Lake  Chicago.    Calumet  stage 75 

19.  Map  of  the  district  between  Riverside  and  Summit 77 

20.  Map  of  part  of  Lake  Cliicago.    Toleston  stage : 80 

21.  Diagram  showing  the  development  of  a  straight- walled,  dat- floored  valley 84 


'♦' 


IX 


LETTER  OF  TRANSMITTAL. 


State  Geological  Survey^ 

University  of  Illinois,, 

Urbana,    March   22,    1909. 
Governor  C.  S.  Deneen,  Chairman,  and  Members  of  the  Geological  Com- 
mission : 

Gentlemen — I  submit  herewith  a  report  on  the  Physical  Features  oi: 
the  Des  Plaines  Valley  with  the  recommendation  that  it  be  published  as 
Bulletin  11  of  the  Survey.  This  forms  the  second  of  the  "Educational 
Bulletins"  of  the  Survey  being  prepared  under  the  general  direction  of 
R.  D.  Salisbury,  Consulting  Geologist  of  the  Survey.  The  author,  Dr.  J. 
W.  Goldthwait,  now  of  Dartmo  itb  College,  prepared  this  while  connected 
with  Northwestern  University.  Into  it  he  has  put  the  accumulated  ex- 
perience of  several  years'  teaching  during  which  the  Des  Plaines  Valley 
was  explored  and  studied  as  a  field  for  illustration  of  the  common  prin- 
ciples of  physiograpby.  While,  therefore,  the  report  will  be  of  ]-)articular 
interest  to  people  living  in  the  vicinity,  it  will  afford  excellent  illustrative 
material  wherever  rivers  and  their  valleys  are  being  studied.  The  large 
demand  for  the  preceding  bulletin  of  this  series  (Bulletin  7)  indicates 
a  very  widespread  and  live  interest  in  the  subject  of  physical  geography 
among  teachers  and  laymen.  An  intelligent  insight  into  one's  environ- 
ment is  the  desire  of  every  normal  person  and  it  is  felt  that  these  little 
bulletins  serve  a  very  real  need  even  of  those  not  concerned  with  teach- 
ing. Dr.  Goldthwait's  stuclies  of  the  development  and  history  of  this.  ;i 
typical  stream  of  our  region,  with  his  special  notes  on  its  floods,  ha\e 
also  a  very  direct  and  practical  value  in  view  of  the  area  of  land  sibject 
to  overflow  and  the  need-  for  regulation  of  the  stream. 

In  the  preparation  of  the' text  and  illustrations  free  use  has  been  made 
of  earlier  publications  and  the  author  desires  that  acknowledgments  be 
made  especially  to  Messrs.  Frank  Leverett  and  W.  C.  Allen  of  the  U. 
S.  Geological  Survey,  and  Mr.  Lyman  E.  Cooley,  Civil  Engineer,  of  Chi- 
cago. A  copy  of  the  well  executed  map  of  Cook  county,  drawn  for  the 
Sanitary  District  of  C'hicago,  was  furnished  the  author,  through  the 
courtesy  of  the  Chief  Engineer,  Mr.  Isham  Randolph,  and  has  been  of 
great  value.  Small  portions  of  this  map  have  been  copied  in  reduced 
form  in  Figs.  17  and  19.  Mr.  J.  W.  Ferris  of  Joliet  contributed  useful 
information  concerning  the  fossils  of  that  vicitnity.  To  Mr.  J.  M.  Large, 
instr.ictor  in  physical  geography  in  the  Joliet  township  high  school,  the 
—3b  G 


writor  is  indelitcd  for  ;i  cnntruir  niaii  of  tlu'  raviiu'  in  Rood's  woods.  This 
iiiaj)  was  oxtoiidod  and  ivdrawn  to  form  Plate  7  by  ]\lr.  D.  F.  Higgins. 
who  also  prepared  a  contour  map  of  the  gorge  of  Sugar  creek  (Plate  6) 
and  allied  greatly  in  the  ])reparing  of  other  illustrations.  Special  ac- 
knowledgment is  due  to  ]\Ir.  Charles  E.  Docker  for  efficient  help  in 
the  iield,  and  to  I'rofessor  I{.  D.  Salisbury  for  kindly  yet  most  thorough 
criticism. 

The  Survey  is  under  groat  oldigations  to  these  jjontlemen.  and  to  Dr. 
Goldthwait  for  the  projiaration  of  the  report,  all  of  which  it  is  a  ])loasur(' 
to  acknowledge.  Very  respectfully. 

H.  Foster  Bain, 

Director. 


PHYSICAL    FEATURES    OF    THE    DES  PLAINES 

VALLEY. 

(By  James  Walter  Goldthwait.) 


CHAPTER  I. 
GEOGEAPHY  AND  HISTOEY  OF  THE  DES  PLAINES  EIVEE. 

IXTRODUCTIOA'. 

The  Des  Plaines  valley  is  one  of  peciiliar  interest  geologically  and  his- 
torically. The  lower  portion  of  the  valley,  southwest  of  Chicago,  was 
once  occupied  ))y  a  great  river,  the  outlet  of  an  early  Lake  Michigan. 
The  divide  over  which  the  lake  once  spilled  to  the  Des  Plaines,  now  the 
continental  divide  between  the  Laurentian  lakes  and  the  gmlf,  is  only 
about  ten  feet  above  the  present  lake.  So  low  and  flat  is  this  divide  that 
before  the  construction  of  the  Illinois-Michigan  canal  it  Avas  covered  by 
the  spring  freshets  of  the  upper  Des  Plaines,  and  afforded  the  early 
French  explorers  an  easy  and  continuous  canoe  route  from  the  lakes 
to  the  Mississippi.  The  Chicago  pass  is  fully  175  feet  lower  than  the 
next  lowest  pass  in  the  St.  Lawrence-Mississippi  divide,  at  Ft.  Wayne, 
Indiana.  No  wonder  that  the  idea  of  an  artificial  channel  near  Chicago, 
to  Join  the  lakes  with  the  Mississippi,  was  conceived  by  Louis  Joliet, 
one  of  the  first  men  to  cross  the  divide.  The  plan  thus  early  suggested 
was  at  length  realized  in  1848,  when,  after  years  of  delay,  the  Illinois- 
Michigan  canal  was  completed  and  opened  to  traffic.  Again,  when  the 
city  of  Chicago  had  outgrown  its  drainage  facilities,  the  valley  was  re- 
sorted to  for  the  great  sanitary  canal  of  Chicago.  Eich  in  historic  as- 
sociations, and  inevitably  connected  with  the  great  metropolis,  the  Des 
Plaines  valley  is  destined  to  become  of  the  highest  commercial  import- 
ance; for  it  now  awaits  the  constraction  of  a  deep  waterway  that  shall 
conduct  lake  vessels  across  Illinois  to  the  Mississippi. 

Thus  the  valley  of  the  lower  Des  I'laines  possesses  in  a  peculiar  sense 
elements  of  a  strictly  geographic  value.  In  its  physical  features  lie  the 
reasons  for  its  early  discovery  and  exploration,  its  present  industrial 
advantages,  and  its  future  development. 

It  is  not  within  the  province  of  this  report  to  dwell  unon  the  geog- 
raphy of  the  valley — the  relationships  between  the  physical  features  and 
the   historical    and    industrial    conditions — however    interesting   such    a 


THE    DES  PLAINES    VALLEY. 


[BULL.    NO.   11 


Fig.  1.  Map  of  the  Des  Plaines  basin  and  vicinity.  The  distribution  of 
glacial  drift  is  taken  from  Leverett's  map  in  Monograph  3S,  U.  S.  Geol.  Surv.  (in 
Illinois),  and  from  Alden's  map  in  Prof.  Paper  34,  U.  S.  Geol.  Surv.   (in  Wisconsin). 


GOLDTHWAIT.]  GEOGRAPHY   AND    HISTORY.  '6 

story  may  be.  Eather  is  it  the  purpose  here  to  describe  the  physical 
features  and  to  explain  the  manner  in  which  they  have  been  developed. 
The  valley  abounds  in  phenomena  which  would  be  of  interest  to  many 
persons  living  near  by,  and  of  especial  use  to  students  of  physical  geog- 
raphy and  geology  in  the  schools.  Before  presenting  this  material,  it 
will  not  be  out  of  place  to  take  a  general  view  of  the  river  basin  and  the 
Des  Plaines  river,  and  to  outline  briefly  its  history. 

THE  DES  PLAINES  BASIN. 

The  long  narrow  basin  of  the  Des  Plaines  river  (see  Fig.  1.)  lies  only 
a  few  miles  west  of  Lake  Michigan,  in  the  northeast  corner  of  Illinois. 
From  northern  Kenosha  county  in  Wisconsin  southward  through  Lake, 
Cook,  DuPage  and  Will  counties  in  Illinois,  the  basin  has  a  length  of 
ninety  miles.  Its  width,  however,  is  never  over  twenty-five  miles,  and 
for  a  large  part  of  the  distance  is  less  than  fifteen.  Its  area  is  about 
1,400  square  miles. 

The  northern  portion  of  this  basin  is  narrow,  and  is  drained  almost 
wholly  by  the  trunk  river  and  a  single  tributary.  Salt  creek.  Its  area 
(above  Summit)  is  about  634  square  miles.  The  southern  portion  is 
wider  and  more  complex,  for  it  includes  the  north-south  basin  of  the 
Du  Page  river,  the  largest  tributary  of  the  Des  Plaines,  and  several, 
rather  long  creeks  from  the  east.  A  few  miles  below  the  mouth  of  the 
DuPage,  the  Des  Plaines  unites  with  the  Kankakee  to  form  the  Illinois 


river. 


The  elongated  form  of  the  Des  Plaines  basin  is  largely,  if  not  wholly 
dependent  on  the  disposition  of  glacial  drift.  At  the  close  of  the  glacial 
period,  when  the  district  finally  emerged  from  beneath  the  waning  ice 
sheet,  the  bed  rock  had  been  concealed  by  an  irregular  blanket  of  loose 
earthy  material  or  "drift,^'  deposited  in  part  by  the  glacier  itself  and 
in  part  by  the  waters  that  came  from  it.  Conspicuous  among  the  newly 
built  surface  features  was  a  broad  U-shaped  belt  of  rolling  ground,  stand- 
ing a  little  above  its  surroundings,  and  encircling  the  south  end  of  Lake 
Michigan  through  Illinois,  Indiana  and  Michigan.  This  belt  is  known 
as  the  Valparaiso  moraine.  The  manner  in  which  it  was  built  up  around 
the  edge  of  a  lobe  or  tongue  of  ice  which  lingered  in  the  lake  basin  will 
be  explained  in  a  later  chapter.  It  is  enough  here  to  note  that  the  great 
moraine  is  crossed  obliquely  by  the  Des  Plaines  river  between  Summit 
and  Joliet,  and  that  from  its  slopes  comes  a  large  part  of  the  water 
discharged  by  the  river.  The  Valparaiso  morainic  belt  is,  in  fact,  a 
system  of  parallel  ridges;  (1)  a  central  ridge  which  makes  up  the  main 
body  of  the  moraine;  (2)  an  outer  ridge,  lower  or  narrower,  which 
divides  the  Du  Page  basin  from  the  Des  Plaines  proper,  north  of  Joliet, 
and  which  for  several  miles  southwest  of  Joliet  is  separated  from  the 
main  moraine  by  a  crescent-shaped  plain  and  (3)  an  inner  ridge,  lying 
east  of  the  central  belt,  and  separated  from  it  by  the  basin  of  Salt  Creek. 

Just  outside  the  Valparaiso  morainic  system  is  another  border  mor- 
aine, known  as  the  Minooka  till  ridge,  which  forms  the  west  boundary 
of  the  Du  Page  basin,  and  ends  interruptedly  near  the  junction  of  the 


4  THE    DES  PLAINES   VALLEY.  [BULL.  xo.  li 

Des  Plaines  and  Kankakee.  On  tlie  inside  of  the  Valparaiso  moraine, 
near  Lake  Miehigau,  is  a  group  of  till  ridges  called  the  "lake-border 
morainic  system."  Southwest  of  Chicago  these  are  absent;  but  near 
Oak  Park  one  of  them  appears,  and  runs  northward  into  Wisconsin, 
l)eing  joined  on  the  way  by  others  of  the  system  whose  south  ends  are  at 
\Yinnetka  and  Northfield.  Since  tliese  till  ridges  both  branch  and 
coalesce  as  they  run  nortli\vard,  the  number  of  distinct  morainic  lines  at 
different  points  is  variable.  In  northern  Cook  county  it  is  three,  in  Lake 
countv  two,  and  in  Kenosha  countv,  Wisconsin  live. 

Surrounding  the  city  of  Chicago,  between  the  curving  Valparaiso 
moraine  and  the  lake,  is  the  crescent-shaped  Chicago  plain.  It  is  the 
smooth  floor  of  an  extinct  Lake  Chicago,  which  for  a  long  time  occupied 
the  space  between  the  morainic  ridge  and  the  melting  ice  lobe.  Its 
former  border  is  marked  by  abandoned  beach  ridges  and  wave-cut  banks, 
and  its  surface  is  somewhat  diversified  by  similar  shore  forms  built  at 
lower  levels  as  the  lake  fell  from  its  original  height  down  to  the  present 
stage.  On  its  north  side  the  lake  plain  finds  extension  in  a  flat  depres- 
sion which  separates  the  Valparaiso  moraine  from  the  west  till  ridge, 
and  constitutes  the  present  valley  of  the  upper  Des  Plaines. 

Let  us  n6\v  follow  the  Des  Plaines  from  its  source  among  the  till 
ridges  of  Wisconsin  southward  along  the  shallow  inter-morainic  depres-" 
sions  across  a  corner  of  the  Chicago  plain,  and  on  through  the  Val- 
paraiso moraine  b}'  way  of  the  old  outlet. 

THE  DES  PLAIXES  EIVER. 

The  Des  Plaines  issues  from  a  flat  swamp,  or  slough,  near  the  bound- 
ary of  Racine  and  Kenosha  counties,  Wisconsin,  where  drainage  is  so 
imperfect  that  in  wet  weather  part  of  the  marsh  discharges  northward 
to  Eoot  river  and  part  southward  to  the  Des  Plaines.  From  this  ill- 
defined  divide  the  little  stream  runs  south  along  the  depression  which 
separates  the  two  westernmost  of  the  lake-border  till  ridges,  gathering 
drainage  from  other  creeks  among  the  morainic  hollows,  turning  to  run 
eastward  for  a  few  miles  in  Kenosha  count)^  then  resuming  a  southerly 
course  and  entering  Illinois  betAveen  the  two  till  ridges  which  at  that 
point  compose  the  whole  lake-border  system.  West  of  Waukegan  (near 
Gurnee  station)  the  river  passes  through  the  west  ridge ;  and  thence  south- 
ward past  Libertyville,  Wlieeling,  Franklin  Park  and  Maywood,  it  fol- 
lows the  broad  inter-morainic  basin  immediately  east  of  the  Valparaiso 
moraine.  P^ntering  tlie  Chicago  plain  by  way  of  this  Ijroad  pass,  which 
is  in  itself  an  arm  of  the  lake-plain  nearly  shut  off  by  a  long  sand  spit  at 
Oak  Park,  the  river  winds  around  a  beach  ridge  at  Riverside,  swinging 
again  eastward  around  a  rock  elevation  at  Lyons. 

In  the  distance  of  sixty  miles  from  the  head  of  the  Des  Plaines  to  the 
Riverside  dam,  the  river  falls  ninety  feet,  or  at  an  average  rate  of  ly^ 
feet  per  mile.  The  portion  in  Lake  county  has  a  moderately  uneven 
grade,  for  the  river  flows  through  a  series  of  flat,  marshy  stretches  separ- 
ated by  more  pronounced  slopes.  Through  Cook  county  its  fall  is  much 
more  uniform,  since  it  has  entrenched  itself  in  a  vallev,  and  built  a 


GOLDTHWAIT.]  GEOGRAPHY    AND    HISTORY.  D 

well-graded  flood  plain.  From  Eiverside  down-stream  for  three  miles, 
the  Des  Plaines  descends  fourteen  feet  on  the  exposed  ledges,  or  about 
five  feet  per  mile,  to  the  Ogden  dam.  At  this  point  it  lies  within  ten 
miles  of  Lake  Michigan,  and  is  less  than  twelve  feet  above  it.  For  a  de- 
tailed map  of  this  vicinity,  see  Fig.  19. 

Here,  then,  near  Summit,  is  the  divide  between  the  lakes  and  the 
Gulf,  the  St.  Lawrence  and  the  Mississippi.  In  time  of  flood  a  large 
portion  of  the  Desplaines  discharges  over  the  dam  and  through  a  ditch 
to  the  Chicago  river  and  the  lake,  while  the  remainder  follows  the  lower 
Des  Plaines  down  to  the  Illinois  and  Mississippi  rivers.  This  double 
discharge  was  operative  under  natural  conditions  before  the  Ogden  dam 
was  built.  The  natural  divide  was  five  miles  farther  east,  near  Kedzie 
avenue,  at  the  east  end  of  a  great  swampy  tract,  known  as  Mud  lake.  So 
flat  is  the  plain  at  this  point  that  the  escape  of  the  Des  Plaines  from 
the  lake  plain  westward  through  the  deep  notch  in  the  moraine  seems 
highly  accidental. 

From  Summit  it  makes  for  the  head  of  the  abandoned  channel  of  the 
"Chicago  outlet''  where  the  waters  of  Lake  Chicago  once  poured  across 
the  moraine  toward  the  Illinois  valley.  With  imcertain  course,  the  river 
runs  for  a  long  distance  on  the  flat  channel  floor.  This  stretch  between 
Summit  and  Lemont  is  known  as  the  '"12-mile  level."  Since  the  con- 
struction of  the  sanitar\'  canal,  the  Des  Plaines  is  confined  to  an  artificial 
channel  by  earthworks.  Approaching  Lemont,  the  river  finds  bed  rock 
rising  to  the  level  of  the  valley  floor,  and  still  higher  on  either  side  in 
rock  bluffs.  Near  the  left  bank  of  the  Des  Plaines  and  parallel  to  it 
down  the  outlet,  run  the  Illinois-Michigan  canal  and  the  Chicago  drain- 
age canal.    Both  of  them  are  largely  cut  in  solid  limestone. 

Beyond  Lemont  the  rock  declines  again  to  about  the  level  of  the  valley 
floor,  and  the  channel  is  cut  through  the  thick  till  structure  of  the . 
moraine.  Bending  southward,  the  river  runs  past  Eomeo ;  and  now  there 
appear  at  the  top  of  its  bluffs,  terrace  remnants  of  an  old  outwash  plain 
or  valley  train — the  original  fllling  of  the  valley,  deeply  trenched  by 
the  outlet.  At  Eomeo  the  Des  Plaines  begins  to  descend  a  long  series  of 
shallow  rapids,  which  lower  it  eighty  feet  in  the  ten  miles  to  Joliet  pool. 
At  Lockport,  on  the  old  canal,  and  farther  down,  near  Joliet,  are  three 
locks,  made  necessar}^  by  the  rapids.  One  of  them  is  pictured  in  Plate  2. 
Here  the  bed  rock  rises  some  thirty  or  forty  feet  above  the  floor  in 
bluffs  on  both  sides  of  the  valley,  forming  a  flat  rock  terrace  twenty  feet 
lower  than  the  fragments  of  the  outwash  plain.  These  two  terraces,  the 
one  of  gravel  and  sand  of  the  outwash,  and  the  other  of  rock,  mark 
important  steps  in  the  history  of  the  river,  and  of  lake  Chicago  of  which 
it  was  the  outlet.  At  Joliet,  the  river  is  conflned  artificially,  passing 
through  the  west  side  of  the  city.  A  single  dam  crosses  it  at  Jackson 
street.  Below  Joliet  the  descent  of  the  river  is  steep  for  two  or  three 
miles  to  Brandon's  bridge,  where  it  broadens,  forming  Joliet  pool. 

This  pool,  otherwise  known  as  "Lake  Joliet,"  occupies  a  broad,  shal- 
low depression  (ranging  to  ten  feet  in  depth)  in  the  floor  of  the  old 
outlet.  It  extends  five  miles  down  the  valley,  below  Brandon's  bridge, 
allowing  the  river  no  perceptible  fall  in  that  distance.    The  level  of  the 


b  THE    DES  PLAINES   VALLEY.  [BULL.  NO.  11 

river  here  is  about  seventy-six  feet  below  Lake  Michigan.  The  pool  is 
probably  due  to  a  deepening  of  the  floor  of  the  ancient  river,  where  it 
passed  from  the  hard  Niagara  limestone  out  on  to  the  weaker  limestones 
and  shales  of  the  Cincinnati  formation. 

Below  Joliet  pool,  the  slope  of  the  river  is  again  moderate  for  three 
miles.  Just  beyond  the  mouth  of  the  Du  Page  river  another  pool — 
"Lake  Du  Page"' — is  entered.  This  is  ninety  feet  below  Lake  Michigan, 
and  extends  three  miles  down  the  valley.  Half  a  mile  below  it,  the  Des 
Plaines  joins  the  Kankakee,  at  the  head  of  the  Illinois  river. 

HISTORY    OF    THE    CHICAGO    PORTAGE   AND    THE    CAXALS. 

The  divide  between  the  Des  Plaines  river  and  Lake  Michigan  stands 
only  592  feet  above  the  sea — less  tliau  twelve  feet  above  the  present  lake. 
It  is  a  part  of  the  floor  of  the  extinct  Lake  Chicago  which  is  so  flat  as 
to  show  no  slope  to  the  e3-e.  Before  the  natural  drainage  of  the  district 
was  disturbed  by  trenches  and  canals,  the  divide  was  a  broad,  swampy 
tract,  called  Mud  lake;  a  long  slough  west  of  Kedzie  avenue  which  in 
time  of  flood  led  a  part  of  the  water  from  the  Des  Plaines  river  east- 
ward to  the  west  branch  of  the  Chicago  river  and  Lake  Michigan.  In- 
deed, this  slough  may  at  no  very  remote  time  have  carried  the  entire  dis- 
charge of  the  Des  Plaines  river.  It  was  evidently  a  familiar  path  for  the 
Indians,  who  in  time  of  flood  might  paddle  their  canoes  continuously 
from  the  Chicago  to  the  Des  Plaines. 

An  entertaining  and  instructive  account  of  the  early  exploration  of 
this  region  by  the  French  traders  and  missionaries  is  to  be  found  in 
Parkman's  "LaSalle  and  the  Discovery  of  the  Great  West."  In  1671, 
LaSalle  started  out  in  search  of  the  Mississippi.  Sailing  through  Lakes 
Erie  and  Huron,  and  entering  Lake  Michigan,  he  proceeded  southward 
past  the  head  of  Green  bay.  Turning  towards  the  west  at  a  "tres-beau- 
havre,"  which  Parkman  thinks  may  have  been  the  mouth  of  the  Chi- 
cago river,  he  crossed  to  a  river  that  flows  westward — doubtless  the  Illi- 
nois. The  fact  that  LaSalle  chose  the  Chicago  portage  on  a  later  ex- 
pedition, in  1683,  lends  strength  to  the  belief  that  this  was  his  route 
in  1671.     If  so,  he  was  the  first  white  man  to  cross  the  divide  at  Chi- 


cago. 


In  1673,  the  intrepid  explorer  Joliet  and  his  Jesuit  companion  Mar- 
quette, returning  from  their  successful  voyage  of  discovery  on  the  Missis- 
sippi, followed  up  the  Des  Plaines  and  across  the  portage.  In  August, 
1674,  Joliet,  in  a  letter  to  Father  Dablon,^  states  that  "by  cutting  half 
of  a  league  of  prairie"  between  the  "Lake  of  Illinois"  (Lake  Michigan) 
and  the  "Saint  Louis  river"  (the  Illinois)  an  easy  boat  route  would  be 
made  between  the  lakes  and  Florida.  In  1673-4,  Marquette,  on  his  way 
from  Green  Bay  to  the  Mississippi,  where  he  hoped  to  found  a  new 
mission,  was  forced  by  illness  to  spend  the  winter  at  Chicago.  With 
his  two  French  comrades,  he  built  a  cabin  beside  the  west  fork  of  the 
south  branch  of  Chicago  river,  near  the  present  Eobey  street.  On  the 
last  day  of    !March  he  was    driven  away  by  a  spring    freshet    and    ice 

1  Quoted  by  L.  E.  Cooley,   in  "The  Lakes  and  Gulf  Waterway" — report  by  the 
Internal  Improvement  Commi.sslon   of  Illinois  to  the  Governor,   Feb.    1907,   p.   3. 


GOLDTHWAIT.J  GEOGRAPHY   AND    HISTORY.  • 

gorges  on  the  Des  Plaines,  which  flooded  the  low  ground  in  that  vicinity. 
He  crossed  the  divide  on  March  31st,  in  canoes,  and  went  down  the 
Illinois  river  as  far  as  Utica.  Compelled  by  broken  health  to  return 
just  as  his  hopes  were  being  realized,  Marquette  died  on  his  way  up  the 
east  side  of  Lake  Michigan. 

In  the  winter  of  1679-1680,  LaSalle  crossed  the  neighboring 'divide 
at  the  St.  Joseph  river,  and  went  down  the  Kankakee  and  Illinois  rivers 
to  Peoria.  Eeturning  a  few  months  later,  he  followed  up  the  Des  Plaines 
as  far  as  Joliet,  but  chose  thence  an  overland  route  eastward — a  more 
direct  course  for  Fort  Miami.  Again  in  January,  1682,  LaSalle,  ac- 
companied by  Friar  Hennepin,  by  Tonty,  his  Italian  lieutenant,  and  by 
some  fifty  Frenchmen  and  Indians,  journeyed  from  "Checaugou"  across 
the  divide  and  down  the  frozen  Des  Plaines  on  sledges,  to  Peoria.  There 
they  found  open  water,  and,  launching  their  canoes,  floate'd  down  the 
Illinois  and  Mississippi  nearly  to  the  Gulf.  Eeturning  late  the  same 
year,  LaSalle  established  Fort  Saint  Louis  at  Starved  Rock,  opposite 
Utica,  remaining  in  that  vicinity  a  year  and  then  returning  to  France. 
■  La  Salle's  attempt  to  find  the  Mississippi  from  the  Gulf  of  Mexico  in 
1687  failed.  He  was  assassinated  in  Texas  by  members  of  his  party.  The 
fugitives,  together  with  Tonty  (who  had  been  in  charge  of  Fort  Saint 
Louis)  made  their  way  across  the  Chicago  portage  in  1688,  en  route  to 
France. 

Messrs.  E.  Graham  and  Joseph  Phillips  are  quoted  by  Mr.  Cooley  in 
his  recent  report^  to  have  written  in  1819  the  following:  "The  route  by 
Chicago  as  followed  by  the  French  since  their  discovery  of  the  Illinois 
presents  at  one  season  of  the  year  an  uninterrupted  boat  communication 
of  six  to  eight  tons  burden  between  the  Mississippi  and  the  Michigan 
lake;  at  another  season  a  portage  of  two  miles;  at  another  a  portage  of 
seven  miles,  from  the  bend  of  the  Plein  (Des  Plaines)  to  the  arm  of  the 
lake;  and  at  another  a  portage  of  fifty  miles  from  the  mouth  of  the 
Plein  to  the  lake,  over  which  there,  is  a  well  beaten  wagon  road.  Boats 
and  other  loads  are  hauled  by  oxen  and  vehicles  kept  for  tha:t  purpose  by 
French  settlers  at  Chicago."  ,    ,  _ 

Since  the  opening  of  the  Illinois-Michigan  canal,  in  1848,  when  the 
Mud  lake  slough  was  first  tapped  and  drained  by  a  ditch,  several. similar^ 
trenches  have  been  excavated,  at  public  and  private  expense,  and  a  dam 
erected  west  of  the  slough,  close  to  the  Des  Plaines,  as  a  substitute  for 
the  ridge  of  the  divide.  (See  Fig.  19).  Still,  in  time  of  flood,  the 
Des  Plaines  overflows  the  Ogden  dam,  and  the  slQugh  is  filled  with 
water.  .     :  .    ■ 

The  project  of  a  ship  canal  across  the  Chicago  portage  was  laid  before 
congress  by  Albert  Gallatin,  in  his  famous  report  of  1808,  on  means  pf, 
internal  communication.  A  few  years  later  it  was  recommended  tp 
congress  in  a  bill  along  with  the  Erie  canal.  While  the  latter,  thanks, 
to  the  perseverance  of  DeWitt  Clinton,  was  soon  undertaken,  and  finishesd' 
in  1825 — a  "ditch"  running  360  miles  across  ISTew  York  state — the 
Illinois-Michigan  canal  was  long  delayed.     Although  it  was  commenced 


1  Op.   clt.,   p.    5. 


S  THE    DES  PLAINES    VALLEY.  [BUl.i..  no    11 

in  1836,  it  was  not  until  1848,  when  railways  were  already  replacing 
canals  elsewhere,  that  the  Illinois-Michigan  canal  was  finished,  with 
the  summit  level  across  the  Chicago  divide  eight  feet  above  low  water 
mark  of  the  lake.  Water  was  supplied  by  ''the  feeder"  through  the 
'-'sag''  (a  broad  valley  tributar}-  to  the  Des  Plaines  above  Lemont),  and 
in  times  of  low  water  by  lift  wheels  at  Bridgeport.  Its  length,  down 
to  its  termination  at  LaSalle,  was  nearly  a  hundred  miles;  its  vertical 
descent  almost  150  feet.  Two  locks  were  required  near  Lockport,  and 
two  at  Joliet.  The  canal  was 'made  six  feet  deep,  sixty  feet  wide  at  the 
surface  and  thirty-six  feet  at  the  bottom  in  earth,  and  forty-eight  feet 
wide  in  rock.  It  cost  the  State  and  the  city  of  Chicago  about  $10,000,- 
000.00,  only  one-tenth  the  cost  of  the  Erie  canal;  and  two-thirds  of  this 
was  paid  by  a  land  grant.^ 

The  failure  of  the  government  to  properly  dredge  the  Illinois  river 
below  LaSalle  greatly  limited  the  development  of  the  canal.  While 
the  Erie  canal,  profiting  by  the  improvement  of  the  Hudson,  was  a 
vitalizing  artery  of  commerce  for  the  city  of  Xew  York,  the  Illinois 
canal,  too  small  for  lake  boats  and  leading  to  a  barely  navigable  river, 
contributed  only  in  a  moderate  degree  to  the  growth  of  Chicago.  In 
1885  it  was  estimated  that  the  canal  had  saved  the  people  of  Illinois 
$180,000,000.00  in  freight  charges." 

The  plan  of  supplying  the  canal  from  Lake  Michigan — restoring  in 
miniature  the  ancient  outlet  of  Lake  Chicago,  was  not  carried  out  until 
1871,  when  the  city  of  Chicago  cut  down  the  summit  level  for  sanitary 
purposes.  For  the  first  time  in  probably  several  thousand  years,  waters 
flowed  out  from  Lake  Michigan  to  the  Mississippi.  Meanwhile,  the 
federal  and  State  governments  sjient  a  considerable  amount  of  money 
in  constructing  locks  and  dams  along  the  lower  Illinois.  Agitation  of 
plans  for  a  deep  waterway  from  the  lakes  to  the  gulf,  continually  re- 
curring, availed  little  against  conservative  reports  and  recommendations 
of  the  United  States  armv  engineers. 

The  extraordinarily  rapid  growth  of  Chicago  soon  made  the  Illinois- 
Michigan  canal  inadequate  for  the  discharge  of  its  sewage.  Early  in 
August,  1885,  a  heavy  flood  on  the  Des  Plaines  swept  the  sewage  of  the 
city  out  into  the  lake ;  and  the  pollution  of  the  city  water  supply  was 
so  intolerable  that  steps  were  at  once  taken  to  remedy  the  drainage  con- 
ditions. Plans  were  gradually  formed  for  a  new  sanitary  canal.  The 
construction  and  operation  of  this  channel  was  delegated  to  a  "Sanitary 
District  of  Chicago,''  under  an  act  adopted  at  the  Xovember  election, 
1889,  the  district  being  organized  the  following  January. 

The  work  of  excavating  the  drainage  canal  was  begun  in  September, 
1892,  and  finished  in  January,  1900.  Its  length  from  the  west  fork 
of  the  Chicago  river  at  Eobey  street  to  the  controlling  works  at  Lock- 
port  was  twenty -eight  miles.  Of  this  a  little  more  than  half  (the 
fifteen  miles  between  Willow  springs  and  Lockport)  was  cut  through 
rock.    Above  Willow  springs  the  channel  was  sunk  wholly  in  unconsoli- 


1  Statement  by  L.  E.  Cooley.     "The  Lakes  and  Gulf  Waterw-ay,  as  Related  to 
the  Chicago  Sanitary  Problem,"  pp.   4  and  7.     1S91. 

2  L.   E.   Coolers   report  of   1907,    rj.    8. 


OOLDTHWAIT]  GEOGRAPHY    AND    HISTOBT.  » 

dated  beds,  mainly  glacial  drift.  The  depth  of  the  canal  is  twenty-four 
feet,  its  bottom  width,  where  in  earth,  202  feet,  and  where  in  rock,  160 
feet.  The  declivity  is  1  to  40,000  in  the  section  above  Willow  springs, 
and  1  to  20,000  below,  giving  a  total  fall  from  the  head  at  Bridgeport 
to  the  controlling  works  at  Lockport  of  about  Sio  feet.  The  Des  Plaines 
river  was  diverted  from  its  natural  channel  by  embankments  between 
Summit  and  Lockport.  Several  large  bridges  were  built,  and  necessary 
improvements  made  on  the  river  below  the  controlling  works.  The  dis- 
charge of  sewage  down  the  new  channel  and  eventually  out  to  the  Mis- 
sissippi past  St.  Louis  aroused  bitter  feeling  in  that  city.  On  the  same 
day  that  the  canal  was  formally  opened  a  bill  of  complaint  was  filed 
in  the  U.  S.  Supreme  Court  in  the  case  of  "State  of  Missouri  against 
State  of  Illinois  and  Sanitary  District  of  Chicago,""  asking  that  the  dis- 
charge of  sewage  be  stopped.  After  six  years  of  expensive  legal  battles 
and  investigations  by  experts,  the  complaint  was  dismissed. 

ISTow  that  the  sanitary  canal  is  again  nearly  outgrown  by  the  great 
city,  repeated  efforts  are  being  made  to  obtain  the  privilege  to  enlarge 
it  and  to  divert  a  larger  volume  of  water  from  Lake  Michigan,  thus  in- 
suring the  proper  dilution  of  the  sewage.  The  extension  of  the  channel 
to  Joliet  and  La  Salle,  and  the  improvement  of  the  Illinois  river  so  as  to 
give  a  deep  waterway  across  the  State  to  the  Mississippi  and  thus  to  the 
gulf,  even  if  not  immediately  possible,  is  none-the-less  inevitable.  Such 
an  attainment  will  fittingly  express  the  enterprise  and  foresight  of  the 
twentieth  century.  The  project  of  Louis  Joliet  of  an  unbroken  path 
for  boats  from  the  lakes  to  Florida  will  at  length  be  fully  realized,  and 
the  Des.  Plaines  valley  will  become  one  of  the  great  avenues  of  inland 
navigation. 


10 


THE    DES  PLAINES   VALLEY. 


[BULL.   NO.   11 


CHAPTER  II. 


THE  STEUCTURE  OF  THE  BED  BOOK. 


DEPOSITION"   OF  PALEOZOIC   SEDIMENTS. 

Nature  and  Age  of  the  Rods. — Beneath  the  loose,  unconsolidated  de- 
posits, chiefly  glacial  "drift,"  which  cover  most  of  the  surface  of  the 
ground  in  this  region,  is  a  firm  rock  foundation.     This  bed-rock  struc- 


i-SOO 


►  250 


5CA  LEVEL- 


-250- 


-500 


•1250 


^^=^ 


V^^?T 


111 


xnr 


i_.i      I    ri 


i'   i     ',    '■- 


I    .1    .   I 


I       1,    \ 


I  I     I,     I ,  J 


'      I      I 


I.     .1  .    1. 


^    I     I     I   I 


I  I  '       T T 


j_l      '      '   -r-' 


-?5a^r===^ 


Feet. 
Niagara  limestone 220+ 

Cincinnati  shale 110+ 


^    Trenton  limestone. 


300- 


St.  Peters  sandstone 210 


E^^L="^-k^  V     Lower  Magnesian  limestone,    including    red  marl   and 
^^^^^^^^^1         shale 395 


y     Potsdam  sandstone,  including  some  red  marl  and  shale..      686+ 


Fig.    2.     Section   of  rocks   In   a   deep  well   at  Lockport.      (After  Alden,   U.   S, 
GeoL    Surv.) 


GOLDTHWAIT.]  STRUCTURE   OF    BED    ROCK.  11 

ture  consists  of  an  nnknown  thickness  of  great  stratified  formations — 
limestones,  shales  and  sandstones  of  comparatively  remote  age.  The 
formations  are  nearl}^  horizontal  in  position,  resting  one  upon  the  other. 
Their  bedded  or  "stratified"  structure,  fragmental  composition  (in  part), 
and  the  marine  shells  which  are  fossilized  in  them,  indicate  clearly  that 
the  rocks  accumulated  as  successive  sheets  of  sediment  on  the  sea  flioor, 
spread  out  in  the  order  of  their  position,  the  oldest  at  the  bottom.  The 
consolidation  of  the  original  clays,  sands,  and  calcareous  muds  into 
firm,  compact  rock  is  due  largely  to  the  cementing  action  of  percolating 
waters,  which  deposited  mineral  substances  in  the  interstices  of  the 
strata.  Consolidation  is  favored,  if  not  actually  affected,  also,  by  the 
pressure  of  overlying  sediments,  including  great  thicknesses  of  strata 
which  formerly  buried  these  but  have  been  wholly  removed  from  the 
region  by  erosion.  From  their  relation  to  overlying  and  underlying  rocks 
in  other  regions,  as  well  as  from  the  relics  of  animal  life  they  contain, 
these  formations  are  known  to  belong  to  early  geologic  periods,  the 
Cambrian,  Ordovician  and  Silurian.  These  constitute  the  first  three 
divisions  of  the  Paleozoic  era. 

The  Cambrian  Period. — During  these  early  periods,  the  central  part 
of  North  America,  including  the  Great  Lake  region,  was  occupied  by 
an  interior  epicontinental  (on  the  continent)  sea.  The  depth  and  extent 
of  this  sea  fluctuated  repeatedly.  The  rising  of  it,  at  certain  times,  with 
respect  to  the  neighboring  lands,  is  believed  to  have  been  due  largely  to 
the  fact  that  the  lands,  exposed  to  the  disintegrating  and  denuding  forces 
of  the  atmosphere  and  running  water,  were  being  reduced  to  lowlands, 
while  the  rock  Avaste  thus  stripped  from  them  was  being  deposited  in 
the  sea,  partly  filling  the  ocean  basins.  The  waters  thus  displaced  would 
rise,  and  even  though  the  actual  change  of  level  might  be  slight,  it 
would  be  enough  to  cause  the  sea  to  transgress  far  over  the  lands, 
because  of  their  greatly  reduced  condition.  Changes  in  relation  of  land 
and  sea  were  doubtless  inspired  also  by  warpings  and  dislocations  of  por- 
tions of  the  earth's  "crust."  While  it  is  clear  that  such  warpings  have 
occurred,  in  abundance,  inasmuch  as  rocks  which  must  once  have  been 
essentially  horizontal  on  the  sea  floor  are  now  found  far  and  wide  over 
the  lands,  in  a  great  variety  of  warped  and  folded  attitudes,  we  cannot 
tell  with  certainty  the  reason  for  the  deformations.  It  may  be  that 
gravity,  or  the  tendency  of  the  earth's  mass  to  crowd  radially  toward  the 
center,  finds  temporary  and  partial  relief  in  the  sinking  in  or  caving  of 
portions  of  the  earth  which  are  excessively  heavy  (the  ocean  floors)  or 
less  firmly  supported  from  beneath  than  the  surrounding  structure.  It 
may  be,  also,  that  the  earth  has  been  cooling  off  for  ages,  and  while  cool- 
ing, contracting ;  that  along  Avith  this  contraction  it  has  been  shrinking, 
and  the  more  rigid  outer  portion  or  "shell"  has  accommodated  itself  to 
the  shrinking  "nucleus"  by  warping  or  wrinkling. 

Some  such  processes  as  these  caused  the  epicontinental  sea,  during  the 
Cambrian  period,  to  creep  gradually  up  over  the  low  interior  of  Korth 
America,  expanding  on  all  sides,  until  by  the  end  of  the  period,  all  the 
central  portion  of  the  continent  and  most  of  the  western  and  north- 
western  portions  were  submerged.  (See  Fig.  3).  An  extensive  highland 
belt,  "Appalachia,"  separated  this  interior  sea  from  the  Atlantic  on  the 


12  THE    DES  PLAINES   VALLEY.  [bull.  no.  11 

oast,  and  long,  discontinuous  mountain  belts  in  the  far  west  and  north- 
west, separated  it  from  the  Pacific.  On  the  north,  a  great  V-shaped 
land  area  in  Canada,  "Laurentia/'  formed  at  that  time  the  main  part  of 
the  land  of  the  North  American  continent.  Two  large  highlands,  out- 
liers of  the  Laurentia  land,  perhaps  escaped  submergence;  one  in  the 
Adirondack  region  of  northern  New  York,  and  the  other  in  the  high- 
lands of  northern  Wisconsin.  Around  their  subsiding  borders  were  spread 
out  in  late  Cambrian  time  extensive  deposits  of  sand.  From  the  Wis- 
consin highland  region  the  sand  reached  southward  on  the  sea  floor  well 
into  Illinois,  and  now  constitutes  the  Potsdam  sandstone,  which  is  pene- 
trated by  a  few  deep  wells  in  and  about  Chicago  (See  Fig.  2). 

The  Ordovician  Period. — During  the  next  geologic  period,  the  Ordo- 
vician,  the  interior  sea  continued  to  expand,  though  local  and  tempor- 
ary oscillations  of  its  floor  and  its  shores  kept  changing  its  outline.  In 
northern  Illinois,  a  change  from  sandy  sediments  to  sandy  limestones 
and  finally  to  pure,  fine-grained  limestones  as  the  Ordovician  period 
progressed  indicates  that  the  surrounding  land  areas  suffered  great  reduc- 
tion under  the  destructive  action  of  atmosphere  and  erosion,  so  that 
during  middle  and  late  Ordovician  the  waters  of  the  interior  sea  were 
no  longer  clouded  by  river-borne  sediment,  and  the  deposits  made  were 
limited  almost  wholly  to  shells,  corals,  and  other  organic  remains.  The 
early  Ordovician  sediments  are  the  Lower  Magnesian  limestone  and  the 
St.  Peter's  sandstone.  Both  are  encountered  by  wells  (See  Fig.  2) .  Above 
them  is  the  Trenton  limestone,  containing  an  abundance  of  fossils,  which 
indicate  that  the  water,  while  relatively  clear,  was  shallow  and  rather 
warm.  The  sea  floor  was  peopled  by  colonies  of  lime-secreting  animals, 
such  as  corals,  brachipods,  trilobites,  and  others  whose  peculiarities  may 
])roperly  be  left  for  fuller  consideration  in  connection  with  the  Niagara 
limestone,  since  that  is  the  only  rock  exposed  to  any  extent  in  the  Des 
Plaines  valley  district. 

Toward  the  close  of  the  Ordovician  period,  the  Trenton  limestone  de- 
posits were  buried  by  a  great  sheet  of  mud,  over  one  hundred  feet  thick, 
which  has  since  been  consolidated  into  the  Hudson  river  or  Cincinnati 
shale.  By  the  time  the  mud  of  this  formation  was  deposited  the  interior 
sea  had  begun  to  shrink,  and  the  surrounding  land  to  emerge,  exposing 
broad  coastal  plains,  from  which  and  across  which  sediment  was  washed 
into  the  sea. 

Geographic  changes  of  large  extent  now  occurred.  Intense  deforma- 
tions in  eastern  New  York  added  to  the  width  of  the  Appalachian  moun- 
tain belt,  while  in  the  Mississippi  valley  region  there  was  a  very  exten- 
sive emergence  of  land,  with,  however,"  little  or  no  deformation  of  the 
rocks.  The  interior  sea  shrank  to  small  proportions  and  marine  life 
became  seriously  restricted.  Many  species  of  animals  were  forced  to 
migrate  to  deeper  parts  of  the  seas,  and  many  were  exterminated.  These 
parallel  changes  of  the  geography  and  the  fauna  are  the  reasons  for 
separating  the  Ordovician  period  from  the  succeeding  Silurian. 

Down  the  Des  Plaines  valley,  about  four  miles  below  Joliet,  and  op- 
posite Flathead  mound,  are  a  few  exposures  of  limestone  near  the  old 
canal,  which  may  be  a  part  of  the  Cincinnati  formation.     The  rock  is 


GOI.DTHWAIT.] 


STKUCTURE   OF    BED    ROCK. 


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14  THE    DES  PLAINES    VALLEY.  [BULL.  NO.  11 

composed  partly  or  argillaceous  (clay-bearing)  limestone,  of  dull  greenish 
or  bluisli  color  (weathering  bull'),  and  partly  of  dense  cherty  beds,  li 
is  an  exceptionally  rich  Held  for  collecting  fossils.  Two  of  tlie  siliceous 
layers  are  full  of  coiled  gastropod  shells  (somewhat  like  No.  7,  Plate  1) 
and  cup  corals  (zaphrentis,  Ko.  3,  Plate  1).  The  latter  are  sometimes 
an  inch  long,  and  stand  out  from  the  weathered  surface  of  the  rock 
because  they  have  been  completely  replaced  by  insoluble  silica.  In  other 
beds  of  the  limestone  are  to  be  found  fragments  of  trilobites  and  brachi- 
opods  and  many  pteropods  (tentaculties).  This  rock  and  its  fossil  con- 
tents are  quite  dill'erent  from  the  Niagara  limestone,  as  exposed  about 
Chicago  and  Joliet;  and  it  is  probably  a  part  of  the  Cincinnati  form- 
ation. 

An  abandoned  quarry  at  the  lower  end  of  ''Flathead"  gives  a  good 
exposure  of  blue  shales  and  shaly  limestones  typical  of  the  Cincinnati 
formation.  Certain  layers  here,  notably  two  or  three  thin  shaly  layers 
on  the  floor  of  the  quarry,  are  full  of  fossils,  especially  strophomena 
(See  No.  9,  Plate  1),  which  are  silicified,  and  show  plainly  on  the 
weathered  surface.  Traces  of  trilobites  (See  No.  5,  Plate  1)  are  evident, 
but  not  sufliciently  well  preserved  to  make  them  of  value  for  collection. 
In  some  of  these  a  film  of  marcasite  (iron  sulphide)  has  replaced  the 
original  shell  structure,  and  has  since  turned  black,  under  exposure  to 
the  air.  Orthoceras  (a  straight  shelled  cephalopod,  (See  No.  4,  Plate  1) 
is  also  plentiful.  No  traces  of  crinoids,  however,  have  been  found. 
Other  exposures  of  the  Cincinnati  formation  are  to  be  seen  at  the  mouth 
of  Rock  run,  and  near  Channahon. 

The  Silurian  Period. — With  the  changes  which  closed  the  Ordovician 
period,  most  of  the  interior  of  the  continent  became  dry  land,  but  as 
the  Silurian  period  advanced,  the  epicontinental  sea  once  more  em- 
croached  upon  a  part  of  the  interior,  perhaps  creeping  southward  from 
Hudson  bay  (See  Fig  4).  It  expanded  over  Illinois  and  Michigan,  and 
southward  and  southwestward  to  Arkansas  and  Missouri,  where  it  was 
presumably  bordered  by  a  land  area.  In  this  area  a  great  limestone 
formation,  the  Niagara  limestone,  was  laid  down.  This  formation  out- 
crops continuously  for  more  than  a  thousand  miles,  from  central  New 
York  to  northeastern  Iowa,  and  is  widely  exposed  about  the  Great  Lakes, 
forming  the  surface  rock  of  the  northeastern  corner  of  Illinois.  It  takes 
its  name  from  the  falls  of  Niagara,  for  which  the  hard  limestone  is 
chiefly  responsible.  Since  this  is  the  only  rock  exposed  in  the  Des 
Plaines  valley,  it  deserves  more  than  brief  mention  here. 

Where  it  has  been  penetrated  by  artesian  wells  in  the  vicinity  of  Chi- 
cago, the  Niagara  limestone  has  a  thickness  of  from  250  to  400  feet.  Its 
original  thickness  was  probably  still  greater,  for  we  cannot  say  how  much 
was  worn  away  from  the  top  of  it  in  the  long  interval  of  exposure  and 
erosion  between  the  Silurian  and  the  glacial  periods,  when  the  rock 
surface  was  finally  buried  by  glacial  drift.  Like  most  limestones,  the 
Niagara  limestones  was  originally  an  organic  deposit — that  it,  an  ac- 
cumulation of  calcareous  skeletons  and  shells  of  marine  animals,  worked 
over  by  the  waves  and  currents,  and  ground  to  a  fine  calcareous  mud. 


GOLDTHWAIT] 


STRUCTUKE   OF    BED    ROCK. 


15 


16  THE   DES  PLAINES   VALLEY.  [BULL.  NO. 


One  of  the  distinctive  features  of  the  Niagara  limestone  is  the  wealth 
of  fossils  it  contains.  Evidently  the  interior  sea  was  nearly  free  from 
river-borne  sediment  in  many  places.  Hence  it  is  believed  the  surround- 
ing lands  were  low,  and  the  rivers  sluggish.  The  water  apparently  was 
warm  and  of  slight  depth — perhaps  not  over  150  feet;  for  several  species 
of  corals  grew  in  great  profusion  and  built  extensive  reefs  like  those  of 
tropical  seas  today.  In  eastern  Wisconsin,  especiall}',  the  reef  build- 
ing habit  was  well  developed,  and  there  it  appears  that  the  coral  reefs 
were  tenanted  by  hosts  of  animals  of  other  orders  such  as  brachiopods 
and  molluscs,  all  of  which  have  contributed  to  the  rock  mass.  Under 
tlie  attack  of  the  waves  these  reefs  suffered  continual  grinding  and  recon- 
struction. The  blocks  and  smaller  fragments  were  piled  up  in  embank- 
ments, while  the  sand  and  finely  ground  clay  was  spread  out  in  broad 
sheets  on  the  sea  floor.  Animal  life,  so  profuse  near  the  reefs,  was  more 
scanty  on  the  broad  smooth  flats  of  white  calcareous  mud  about  them. 
These  calcareous  muds  now  constitute  layers  of  compact,  fine-grained 
gray  limestone,  nearly  barren  of  fossils. 

Some  idea  of  the  variety  of  the  marine  animals  of  the  Niagaran  group 
may  be  gathered  from  Plate  1,  in  which  a  few  of  the  most  characteristic 
types  of  fossils  of  the  Des  Plaines  valley  and  Chicago  district  are  to  be 
seen.  The  resemblance  between  the  fauna  of  northeastern  Illinois  and 
that  of  rocks  about  Hudson  bay,  Grinell  land,  north  Greenland,  and 
noi-thern  Europe,  when  contrasted  with  the  markedly  different  fauna 
of  the  Appalachian  district,  warrants  the  belief  that  the  interior  sea 
extended  northward  from  the  Mississippi  valley  across  Canada  and 
north  Greenland,  and  thence  eastward  and  southeastward  across  Iceland 
to  Scandinavia  and  England.  In  no  other  way  can  we  satisfactorily 
explain  the  inter-migration  of  animals,  whose  habitat  was  the  shallow 
shore  zone.  It  is  evident,  too,  that  the  climate  in  the  northern  hemis- 
phere at  this  time  was  much  more  equable  than  now,  to  enable  the  same 
corals  to  thrive  in  Arctic  regions  and  in  the  lower  Mississippi  valley. 

The  Niagara  limestone,  so  far  as  known,  is  the  bed  rock  beneath  all 
but  the  extreme  southwest  portion  of  the  Des  Plaines  valley.  Not  far 
below  Joliet,  as  previously  stated,  the  Cincinnati  makes  its  appearance 
on  the  valley  floor.  Natural  exposures  of  the  Niagara  occur  on  the  bed 
of  the  Des  Plaines  near  Lyons,  on  the  floor  and  in  the  side  bluffs  near 
Lemont  and  from  Lockport  down  to  Joliet.  On  the  tributary  streams 
small  exposures  occur  frequently  near  the  main  valley,  where  the  side 
valleys  have  been  cut  most  deeply,  e.  g.,  on  Long  run.  Fraction  run  and 
Sugar  creek.  The  limestone  appears  in  the  bed  of  Hickory  creek  at 
New  Lenox,  forming  small  rapids.  A  broad  elevation  of  rock  at  Lyons, 
about  which  the  Des  Plaines  river  runs,  between  Eiverside  and  the  Santa 
Fe  bridge,  is  only  thinly  covered  by  drift.  In  many  places  here,  the 
rock  is  within  a  foot  or  two  of  the  surface,  and  is  exposed  in  shallow  pits 
and'trenchcs  in  the  fields.  Stone  walls  built  of  the  fragments,  in  a  field 
east  of  Joliet  avenue,  contain  an  abundance  of  fossils,  chiefly  crinoids. 

A  good  field  for  collecting  fossils  of  the  Niagara  limestone  is  the 
great  pile  of  refuse  along  the  side  of  the  drainage  canal  near  Lemont. 


STATE  GEOLOGICAL,  SURVEY. 


BULL.   NO.   11,   PL.   1 


Fossils  from  the  Niagara  formation.  Corals — Halycites  (chain  coral),  (2) 
Favosites  (honeycomb  coral),  (3)  Zaphrentis  (cup  coral).  Cephalopod — (4)  Ortho- 
ceras.  Trilobites — (5)  Calymene,  in  foreground,  two  specimens;  Dalmanites,  in 
background.      Brachiopods — (6)    and    (9).      Gastropod — 7.      Crinoid — Roots    (8). 


GOLUTHWAIT.]  STRUCTUEE   OF    BED    ROCK.  1  ( 

The  recently  quarried  blocks-  of  rock,  representing  a  vertical  range  of 
twenty-five  feet  where  the  canal  has  cut  wholly  in  rock,  frequently 
afford  a  wide  variety  of  fossils.  Trilobites  {Cahjmcnc  Niagarensis 
No.  5,  Plate  I)  may  be  collected,  for  instance,  in  the  waste  bank  beside 
the  canal  just  northeast  of  quarry  'No.  1,  a  mile  and  a  half  above  Lemont. 

Perhaps  the  best  known  fossil  in  the  Niagara  is  the  orthoceras,  a  long, 
straight,  cephalopod  shell  (No.  4,  Plate  I.)  While  as  a  rule  it  is  only 
one  or  two  feet  long,  it  attains  sometimes  a  length  of  several  feet. 
Naturally  enough,  it  invariably  lies  with  its  long  axis  parallel  to  the 
bedding  planes — a  position  which  it  would  assume  Avhen  it  fell  upon  the 
sea  floor.  In  this  respect,  it  merely  illustrates  a  rule  that  would  apply 
to  all  fossils  which  have  a  marked  flatness  or- length.  They  all  tend  to 
be  deposited  flat  side  down,  or  with  their  length  in  a  horizontal  position. 
Since  the  bedding  planes  are  planes  of  easy  separation  when  the  rock  is 
quarried,  the  surfaces  of  flagstones  frequently  show  casts  of  the  long 
chambered  orthoceras  shells.  One  can  hardly  walk  three  blocks  in 
Joliet  on  a  sidewalk  of  limestone  slabs,  without  seeing  at  least  one  of 
these  big  shells.  In  the  quarries  about  Joliet,  crinoids,  trilobites,  l)rach- 
iopods,  etc.  may  be  collected,  but  usually  with  difficulty,  since  the  massive 
gray  beds  which  are  so  extensively  used  as  building  stone  are  as  a  rule 
barren.  Fossils  are  more  plentiful  in  the  thin-bedded  portions,  which  are 
not  so  often  quarried.  The  abundance  of  nodules  or  lumps  of  chert,  and 
of  cherty  layers  in  the  limestone  (recognized  by  its  compact  flinty  tex- 
ture and  splintery  fracture,  as  well  as  by  its  superior  hardness)  is  due 
in  part,  at  least,  to  the  burial  of  quantities  of  siliceous  sponges  on  the 
ancient  sea  floor.  Traces  of  the  structure  of  these  sponges  have  been 
found  in  the  chert,  under  the  microscope. 

The  Devonian  Period. — At  the  close  of  the  Silurian  period,  the  emer- 
gence of  large  portions  of  the  interior  of  the  continent  greatly  restricted 
the  inland  sea.  Subsidences  of  the  land  and  expansions  of  the  epicon- 
tinental sea  were  renewed  in  the  Devonian.  By  the  middle  of  the  De- 
vonian period  (Hamilton  epocli),  the  northeast  part  of  Illinois  (at 
least  near  Chicago)  was  again  below  the  sea  (See  Fig.  4).  The  evidence 
of  this  is  not  found  in  broad  exposures  of  Devonian  rocks  (like  the  belts 
of  Niagara  and  Cincinnati)  for  the  Devonian  strata  were  stripped  off 
by  erosion  long  ago.  All  that  remains  to  mark  the  former  existence  of 
Devonian  sediments  about  Chicago  are  small  pockets  of  clay,  containing 
fish  teeth  and  other  fragments  of  Devonian  species,  in  the  cracks,  here  and 
there,  in  the  Niagara  limestone.  The  first  discovery  of  this  interesting 
feature  was  at  a  quarry  near  Elmhurst.  Since  then,  similar  Devonian 
exposures  have  been  found  in  Fred  Schultz's  quarry,  at  Lyons.  Stuart 
Weller"s  description  of  the  Elmhurst  locality  is  quoted  below  in  some- 
what abbreviated  form.^  "At  this  locality  the  limestone  is  much  frac- 
tured by  two  sets  of  gentle  folds  whose  axes  have  a  general  northwest, 
southeast  and  northeast,  southwest  direction,  joint  cracks  being  well 
developed.     Some  of  these  cracks  are  several  inches  in  width,  and  are 


1  "A  peculiar  Devonian  deposit  in  Northeastern  Illinois ;"  Journ.  Geo!.,  vol.   7, 
pp.   483-4S8,  1899. 

—2  G 


18  THE   DES  PLAINES   VALLEY,  [bull.  no.  11 

in  general  filled  Avitli  a  black  or  blue  clay.  At  one  point,  in  the  southeast 
face  of  the  quarry,  about  eighteen  feet  below  the  glaciated  surface  of  the 
rock,  one  of  these  joints  is  somewhat  enlarged,  to  form  a  narrow  tri- 
angular opening  about  six  inches  in  width  at  the  base  and  about  sixteen 
inolies  in  height.  This  opening,  instead  of  being  filled  with  clay,  as  arc 
all  the  other  larger  joints  in  tlie  quarry,  is  filled  with  a  breccia  composed 
of  angular  fragments  of  the  adjacent  limestone,  imbedded  in  a  dark 
brown  arenaceous  matrix.  This  matrix  is  abimdantly  fossiliferous,  con- 
taining iniiiiense  numbers  of  {\^h  teeth  and  a  smaller  number  of  lingula 
shells  and  other  brachiopods,  which  indicate  its  Devonian  age.^^  The  fish 
teeth  represent  a  species  ptyctodns  calceoliis  and  two  new  species  of 
diplodus.  Of  these  the  teeth  of  ptyctodus  are  extremely  abundant.  The 
most  plentiful  brachiopod,  lingula  ligea,  is  known  to  occur  in  the  De- 
vonian of  New  York  and  Xevada.  One  of  the  others,  of  which  only  one 
specimen  was  found,  and  the  teeth  of  diplodus  had  previous  been  known 
only  in  carboniferous  strata.  Apparently,  then,  the  deposit  is  of  very 
late  Devonian  age. 

The  nearest  place  where  the  Devonian  is  the  surface  rock  is  probably 
northwestern  Indiana;  but  there  it  is  almost  wholly  concealed  by  glacial 
drift.  "The  nearest  actual  outcrop  of  Devonian  is  at  Milwaukee,  Wis- 
consin, eighty  miles  north  of  Elmhurst;  and  the  nearest  outcrop  to  the 
west  is  near  Kock  Island,  Illinois,  one  hundred  and  thirty  miles  away.  At 
both  of  these  localities  ptyctodus  calceoliis  occurs,  but  the  strata  are 
believed  to  be  somewhat  older  than  the  material  from  Elmhurst. 

'The  presence  of  this  Upper  Devonian  fauna  at  Elmhurst,  buried  as 
it  is  deep  down  in  the  Niagara  limestone,  indicates  with  certainty  that 
during  the  greater  part  of  Devonian  time  the  region  now  known  as 
northern  Illinois  was  above  sea  level.  It  was  part  of  what  was  probably 
a  large  land  surface,  stretching  from  the  Wisconsin  land  on  the  north 
to  the  Ozark  land  of  Missouri  on  the  south.  The  waters  which  collected 
upon  this  land  surface  in  part  percolated  through  the  underlying  rock 
strata  and  by  solution  increased  the  size  of  many  joint  cracks.  At  a  later 
period,  near  the  close  of  the  Devonian,  when  the  sea  again  occupied  the 
region,  sand  was  sifted  down  into  these  open  joints  and  with  it  the  teeth 
of  fishes  which  inhabited  the  sea  thereabout.  It  is  perhaps  possible  that 
the  opening  which  has  in  recent  time  been  uncovered  at  Elmhurst  was 
during  this  late  Devonian  time  large  enough  for  the  entrance  of  some  of 
these  fish,  and  that  they  sought  this  opening  for  shelter,  much  as  fish  at 
the  present  time  enter  similar  openings. 

"The  manner  of  communication  between  this  opening  and  the  surface 
is  not  clearly  shown  in  the  field,  but  arenaceous  material  with  fragments 
of  fish  toeth  is  seen  clinging  to  the  quarry  face  to  the  left  of  and  above 
the  opeiiing.  This  rock  face  is  one  side  of  a  joint  whose  opposite 
side  has  been  removed,  through  which  there  may  have  been  communi- 
cation between  the  buried  opening  and  the  sea  bottom  above.'^ 

The  similar  exposure  in  the  Lyons  quariT  was  first  observed  and  ex- 
amined about  a  year  ago,  by  Messrs.  C.  E.  Peet  and  Stuart  Weller.    The 


GOLDTHWAIT.]  STEUCTUEE   OF    BED    EOCK.  19 

following  brief  description  of  it  is  written  by  Mr.  Charles  E.  Decker,  who 

visited  the  locality  in  May,  1907,  after  much  of  the  rock  had  been 

quarried  away : 

The  fish  teeth  occur  in  a  tension  crack  near  the  axis  of  a  large  fold  in  the 
south  face  of  the  quarry  (described  later).  When  examined  a  recent  blast 
had  torn  away  several  feet  of  rock  along  the  crevice,  and  some  fragments  of 
teeth  were  found  in  the  debris  among  the  loose  rocks.  The  crevice  is  narrow, 
varying  from  one  to  two  and  a  half  inches  in  width,  and  extends  downward 
about  ten  feet  from  the  top  of  the  quarry.  It  is  filled  with  a  dark,  compact 
clay,  in  which  there  are  many  angular  fi'agments  of  limestone.  ^  The  fossil 
teeth  are  black.  The  largest  one  found  is  about  three-sixteenths  of  an  inch 
in  cross  section  and  three-fourths  of  an  inch  long.  A  small  water-worn 
brachiopod  was  found  in  the  same  crevice,  and  near  the  edge  of  the  crevice, 
a  large  fragment  of  a  blunt  tooth  or  tusk. 

The  close  of  sedimentation. — At  the  close  of  the  Devonian  period, 
northern  Illinois  seems  to  have  emerged  again  from  the  sea.  Whether  in, 
succeeding  periods  it  sank  again  to  receive  new  sheets  of  sediments  can- 
not well  be  determined,  since  later  exposure  to  weathering  and  stream, 
erosion  has  stripped  off  eveiything  down  to  the  Niagara  limestone.  It 
is  possible  that  during  the  Mississippian  and  Pennsylvanian  periods, 
when  thick  limestone  and  the  coal  measures  were  being  deposited  in 
the  central' and  southern  parts  of  the  State,  the  sea  covered  the  north- 
east corner  of  Illinois ;  but,  if  so,  not  a  scrap  of  these  rocks  remains,  so 
far  as  known,  in  the  Des  Plaines  valley.  Even  the  Devonian  sediments 
were  weathered  and  eroded  except  where  they  had  penetrated  deep 
cracks  in  the  underlying  limestone.  By  the  close  of  the  Paleozoic  era 
at  least,  when  the  Appalachian  ranges  were  elevated,  and  the  whole; 
eastern  part  of  the  continent  emerged,  the  district  in  which  the  Des 
Plaines  now  lies  became  dry  land.  Its  rock  structure  was  thus  prac- 
tically completed.  The  constructive  process  of  deiDOsition  ceased,  and 
the  destructive  process  of  denudation  took  its  place. 

WAEPING^    JOINTING    AND    FAULTING    OF    THE    EOCKS. 

The  uplifting  of  the  rock  foimdation  in  a  region  is  never  accomplished 
without  local  warpings  of  the  strata,  extensive  fracturing  of  a  systematic 
sort,  and  more  or  less  definite  dislocation  of  the  rock  along  certain  frac- 
tures. So,  in  the  quarries  and  other  exposures  in  the  Des  Plaines  valley 
the  Niagara  limestone  exhibits  signs  of  having  been  subjected  to  great 
strains,  and  of  having  yielded  in  a  measure  by  the  development  of  folds, 
joints  and  faults. 

Folds. — The  elevation  of  the  Silurian  strata  in  this  district — or,  more 
accurately,  the  elevators,  as  there  have  doubtless  been  several  move- 
ments— seem  to  have  been  pretty  uniform  in  amount,  for  the  bedding  of 
the  rocks  as  a  riile  remains  nearly  horizontal,  or  in  about  the  attitude 
in  which  the  sediments  were  laid  down  on  the  sea  floor.  In  places,  how- 
ever, the  strata  lie  in  an  inclined  position,  with  a  dip  of  10°,  20°,  or 
30°  from  the  horizontal.  In  the  quarries  near  Cass  and  Grinton  streets, 
on  the  east  side  of  Joliet,  dips  of  moderate  amount  can  be  measured.  In 
Dellwood  park,  the  rock  shows  a  general  dip  10°  to  20°  toward  the  south- 


20  THE   DES  PLAINES   VALLEY.  Tbull.  no.  11 

west,  but  there  are  local  iinJulatious  in  the  bedding.  A  good  view  of 
this  can  be  had  just  below  the  upper  dam  on  the  north  wall  of  the  gorge. 
It  is  possible  that  some  of  the  small  folds  or  undulations  are  not  deform- 
ations formed  when  the  rock  was  uplifted  after  Devonian  time,  but  that 
they  are  of  earlier  date.  Folds  of  a  puzzling  nature  and  in  part  at  least 
of  Silurian  age  occur  in  the  quarry  of  Fred  Shultz  at  Lyons. 

The  chief  structural  feature  of  the  Lyons  quarry  is  a  gentle  arch,  or 
anticlinal  fold,  the  axis  of  which  runs  north  and  south.  Cross  sections 
of  it  appear  in  the  quarry  walls  on  both  the  north  and  south  sides. 
Superposecf  upon  this  major  fold  are  domes  and  folds  of  minor  im- 
portance, with  axes  running  in  various  directions.  They  are  best  seen 
along  the  south  side  of  the  quarry,  as  the  strata  on  the  west  side  are 
approximately  horizontal.  The  nature  of  these  folds  presents  an  inter- 
esting problem.  It  might  indeed  be  questioned  whether  they  are  folds 
or  constructional  elevations  formed  at  the  time  of  deposition  of  the 
sediment  which  makes  the  limestone.  In  some  cases  the  folds  affect  only 
a  certain  zone,  the  strata  above  and  below  being  nearly  horizontal.  In 
one  fold  on  the  south  side  and  still  more  notably  on  the  west  side,  the 
beds  thicken  markedly  towards  the  center  of  the  fold.  The  fold  itself 
is  flanked  by  nearly  horizontal  layers,  which  thin  out  against  the  limbs 
of  the  fold  and  are  overlain  conformably  by  continuous  horizontal  beds. 
If  corals  Avere  present  in  sufficient  numbers,  the  arched  structures  might 
be  taken  for  reefs.  The  strata  underlying  the  arch  seem  to  be  crumpled, 
at  the  level  of  the  quarry  floor,  as  if  there  had  been  an  actual  deforma- 
tion. If  so,  it  seems  almost  necessary  to  suppose  that  the  folding  oc- 
cured  while  the  limestone  was  being  deposited,  because  the  arched  beds 
are  overlapped  by  horizontal  beds  without  any  intervening  surface  of 
erosion.  If  we  can  imagine  earth  movements  to  have  folded  the  surface 
sediments  without  raising  them  above  the  sea,  while  deposition  continued, 
we  satisfy  both  the  peculiar  overlapping  and  the  thickening  of  the  beds. 
Soft  plastic  muds  or  ooze  might  be  squeezed  or  thickened  by  compression 
in  the  arches. 

Another  puzzling  relation  of  beds  is  seen  at  the  southeast  side  of  the 
Lyons  quarry,  where  an  anticlinal  bend  at  the  surface  is  directly  over  a 
synclinal  bend,  there  being  a  lens-shaped  mass  between,  with  ill-defined 
bedding  planes. 

A  certain  amount  of  warping  is  going  on  here  at  the  present  time 
where  the  rock  floor  of  the  quarry,  under  long  exposure  has  expanded. 
One  of  these  recent  folds  may  be  seen  on  the  bottom  of  the  quarry  where 
two  layers  have  been  arched  up  so  as  to  leave  several  inches  of  space 
between  them.  The  same  phenomenon  has  been  observed  in  the  quarry 
near  Crystal  run,  north  of.Joliet,  and  doubtless  occurs  elsewhere. 

Joinis. — The  same  Avarpings  Avhich  accompanied  the  elevation  of  the 
strata  to  their  present  positions  involved  tensions  and  strains  which  led 
to  a  wide-spread  and  systematic  cracking  and  jointing  of  the  rocks. 
These  joints  may  be  plainly  seen  in  any  quarry  in  the  Niagara  lime- 
stone. They  are  vertical  cracks  by  which  the  rock  mass  is  divided  into 
rectangular  blocks    (Plate  2).      The  cracks  are    by    no    means    hap- 


GOLDTHWAIT.]  STKUCTUEE   OF    BED    ROCK.  21 

hazard,  but  run  in  sets  or  S3'stems.  Each  set  includes  a  large  number  of 
■  parallel  or  nearly  parallel  joints.  Usually  two  sets  are  more  conspicuous 
than  the  others,  and  these  are  perpendicular  to  each  other.  They  run 
down  to  considerable  depths,  but  just  how  far  is  unknown.  In  width 
they  range  from  closed  fractures  to  gaping  fissures.  The  difference  does 
not  date  back  to  their  origin,  but  is  due  almost  wholly  to  subsequent 
solution  and  weathering,  accomplished  by  the  penetration  of  air  and 
water.  Because  of  this  enlargement  of  cracks,  the  jointing  is  much 
more  conspicuous  near  the  surface  than  near  the  bottom  of  the  quarry. 
Joints  appear  to  be  much  more  numerous  above  than  below.  In  a 
measure  this  is  a  real  as  well  as  an  apparent  truth.  At  the  surface  the 
tensions  due  to  deformation  are  stronger  than  they  are  far  below  ground, 
and  more  cracks  result.  The  jDhotograph  of  the  wall  of  Sugar  creek 
gorge  (Plate  2,  B)  shows  a  natural  exposure  of  joint  surfaces. 

Faults. — Signs  of  dislocation  or  faulting  along  joint  fractures  may 
be  seen  rarely  in  the  Des  Plaines  valley.  Where  a  set  of  stratified  rocks 
is  faulted,  the  relative  motion  on  the  two  sides  will  be  shown  by  the  way 
the  strata  fail  to  match.  Those  on  the  (relatively)  lifted,  side  lie  above 
those  on  the  downthrown  side.  Such  faultings  have  been  very  common 
in  the  past.  They  are  known  to  have  occurred  in  recent  times  and  to 
be  the  chief  cause  of  earthquake  shocks.  The  recent  earthquake  of  San 
Francisco^  was  caused  b}"  a  dislocation  resulting  in  a  horizontal  sliift  of 
from  eight  to  twenty  feet,  with  but  little  vertical  displacement.  A?  a 
result  the  surface  of  the  ground  was  broken,  fences  and  car  tracks  offset, 
and  in  some  places  a  low  fault  "scarj)"  formed.  Even  after  erosion  has 
obliterated  the-surficial  indications  of  a  fault,  its  existence  can  be  told 
from  the  dislocated  structure.  Indeed,  in  most  cases  faults  are  discovered 
in  this  way,  for  as  compared  with  the  rapidly  changing  form  of  the  sur- 
face, underground  structure  is  permanent.  In  the  district  about  the 
Des  Plaines  valley  faults  are  relatively  rare  and  of  small  measure.. 
Occasionally  on  the  wall  of  a  Cjuarry  one  may  see  a  joint  crack  at  which 
there  is  a  break  in  the  continuity  of  strata.  This  seldom  amounts  to 
more  than  a  few  inches. 

The  fault  best  shown  in  this  district  is  near  Joliet.  It  crosses  a  littlo 
gorge  out  by  Sugar  run  between  the  Alton  railway  and  the  slaughter 
house  road.  The  walls  of  this  gorge  are  vertical  joint  faces,  developed 
by  the  tearing  off  of  Ijlocks.  As  usual,  two  joint  systems,  nearly  at  right 
angles,  are  dominant.  On  the  map  of  this  district  (Plate  6)  the  joint 
systems  are  indicated  by  two  crosses.  It  is  worthy  of  notice  Jiere 
that  where  the  limestone  contains  hard  nodules  of  chert  or  flint  the 
joint  cracks  cut  through  them  like  a  knife,  rather  than  pass  around  them 
irregularly.  Obviously,  the  cracks  occurred  after  the  rock  became  thor- 
oughly compact  and  hard.  Scarcely  one  hundred  feet  above  the  bridge 
at  the  slaughter  house  road,  the  fault  shows  in  cross  section  on  the  south- 
east wall  of  the  gorge  (Plate  2,  B.)  Three  cherty  bands  in  the  lime- 
stone mark  out  the  stratification,  and  serve  to  distinguish  the  offset  on 
the  right  and  left  side  of  the  fault  plane,  which  is  one  of  the  master 


iSee  Salisbury,  "Physiography,"   pp.   419-426.     1907. 


22  THE   Di:s  PLAINES   VALLEY.  [bull.  no.  11 

joints  running  northwest-southeast.  The  block  on  the  right  (southwest) 
side  has  risen  fully  a  foot  with  reference  to  that  on  the  left.  On  the 
northwest  side  of  the  gorge  the  continuation  of  this  fault  is  somewhat 
concealed,  but  careful  search  will  discover  the  extension  of  the  same  joint 
plane,  which  is  here  accompanied  by  a  zone  of  cinished  or  "brecciated" 
rock  between  the  dislocated  sides.  Tlie  rock,  though  decayed,  has  not 
wholly  lost  the  half  polished,  half  shredded  surface  produced  by  the 
slipping,  a  surface  known  to  miners  and  geologists  as  "slickensides." 
It  is  not  sufficiently  well  preserved,  however,  to  show  the  exact  direction 
of  the  dislocation. 


STATE  GEOLOGICAL  SURVEY. 


BULL.  NO.   11,  PL.   2. 


A.     Lock  on  the  Illinois-Michigan  Canal,  above  Joliet. 


B.     Fault   in    the   Wall    of    Sugar   Creek    Gorge.      The    fault    fracture    cuts    the 
large  rectangular  opening.     The  block  on  the  right  is  a  foot  above  that  on  the  left. 


GOLDTHWAIT.] 


23 


CHAPTER  III. 


THE  CONCEALED  SUEFACE  OF  THE  BED  EOCK. 

SIGNIFICANCE  OF  THE  BURIED  TOPOGRAPHY. 

Except  in  a  few  places,  as  in  the  bluffs  which  overlook  the  Des  Plaines 
valley  at  Leniont,  Lockport  and  Joliet,  and  where  quarries  have  been 
opened,  the  bed  rock  of  this  region  is  concealed  beneath  a  sheet  of 
glacial  drift  or  of  recent  alluvial  material.  So  few  are  the  exposures 
of  rock  and  so  limited  in  extent,  that  it  is  difficult  from  them  to  form 
a  distinct  picture  of  the  buried  bed  rock  topography.  Some  information 
can  be  gained  from  records  of  wells  where  the  thickness  of  the  drift 
cover  has  been  measured,  yet  these  data  are  very  limited,  and  show  little 
more  than  the  fact  that  the  bed  rock  surface  is  uneven,  having  a  relief 
of  75  or  100  feet  in  short  distances.  The  surface  of  the  rock,  it  ap- 
pears, is  much  more  irregular  than  the  old  lake  plain,  and  fully  as  un- 
even as  the  Valparaiso  moraine ;  yet  the  bed  rock  topography  bears  no 
relation  whatever  to  the  topography  of  the  overlying  drift.  We  can 
form  no  correct  idea  of  the  concealed  rock  surface  from  the  location  and 
extent  of  the  moraine  ridges  or  the  lake  plain. 

It  is  of  deep  significance  that  we  have  in  this  region  the  Niagara 
limestone  of  Silurian  age  overlain  immediately  by  glacial  drift.  Evi- 
dence has  already  been  presented,  in  the  remnants  of  Devonian  sediments 
preserved  in  deep  cracks  of  the  underlying  limestone,  that  a  considerable 
period  of  time  elapsed  after  the  Silurian  period,  during  which  a  shale 
formation  was  deposited  on  the  sea  floor,  and  subsequently,  after  emer- 
gence, was  stripped  off  by  erosion.  It  remains  for  us  now  to  extend  this 
conception  of  the  long  inten^al  of  erosion  which  succeeded  the  Devonian 
period  and  antedated  the  deposition  of  the  glacial  drift,  by  realizing  that 
the  Devonian  formation  belongs  far  back  in  geologic  time  while  the 
glacial  drift  is  of  very  recent  date.  The  time  interval  registered  by  the 
sharply  defined  surface  which  separates  the  eroded  bed  rock  from  the 
imconsolidated  drift  is  enormously  long.  This  is  shown  conclusively  by 
the  occurrence  elsewhere  of  a  great  series  of  formations  younger  than 
the  Devonian  and  older  than  the  glacial  drift.  These  formations  are 
absent  from  northern  Illinois,  either  because  this  region  stood  above  the 
sea  and  so  received  no  sediments,  or  because  if  once  deposited  they  were 


24  THE    DES  PLAINES    VALLEY.  [bull.  no.  U 

subsequently  removed  by  erosion.  In  either  case,  the  time  required  for 
the  deijosition  of  the  formations  which  elsewhere  lie  between  the  De- 
vonian and  the  drift  was  immeasurably  long. 

With  this  brief  mention  of  the  importance  of  the  bed  rock  surface 
as  a  record  of  a  great  interval  of  erosion  we  may  turn  to  the  history  of  it. 

The  bed  rock  topography  has  been  moulded  by  two  agencies;  (a)  by 
running  water  and  the  various  processes  of  weathering,  and  (b)  by  the 
great  ice  sheet,,  which,  by  erosion  and  by  the  deposition  of  drift,  modified 
to  a  considerable  extent  the  form  of  the  surface. 

PRE-GLACIAL  DENUDATION. 

Deductions  from  the  "Driftless  Area." — The  pre-glacial  condition  of 
the  topography  can  be  judged  best  by  the  topography  of  the  driftless 
area  of  northwestern  Illinois  and  southwestern  Wisconsin.  The  rock 
structure  of  that  district  and  the  history  through  which  it  has  passed 
are  comparable  to  the  district  surrounding  the  Des  Plaines  valley,  but  the 
driftless  area,  unlike  the  surrounding  region,  was  never  covered  by  the 
ice  sheet,  so  that  its  pre-glacial  surface  is  preserved,  though  modified 
to  some  extent  by  the  erosion  of  later  time. 

With  the  emergence  of  northern  Illinois  from  the  interior  sea,  prob- 
ably at  the  close  of  the  Devonian,  the  rocks  which  had  been  deposited 
were  exposed  to  agencies  of  decay  and  of  valley  excavation.  In  the 
long  periods  of  time  which  followed,  while  tiie  Coal  Measures  of  Illinois 
and  other  states  were  accumulating;  while  the  Alleghany  mountains 
were  folded,  worn  down  to  a  plain,  and  again  uplifted  and  deeply  dis- 
sected by  erosion :  and  while  the  broad  Coastal  Plain  of  the  Atlantic  sea- 
board and  the  gulf  were  being  built;  during  all  this  time,  the  surface 
of  the  rock  structure  of  northern  Illinois  was  being  lowered  by  erosion. 
Once  at  least  it  was  worn  down  to  an  almost  featureless  plain,  a  "pene- 
plain," a  condition  reached  only  when  the  land  stands  still  for  an  almost 
inconceivably  long  period  of  time,  and  river  systems  are  enabled  to  com- 
plete their  work  of  reducing  the  entire  systems  of  their  basins  to  a  low- 
land near  sea  level.  At  length  this  base  leveled  plain  was  lifted  up  by  a 
broad  warping  movement,  while  the  revived  rivers  sank  their  channels 
below  the  rising  plain  and  a  new  set  of  valleys  was  worked  out.  Grad- 
ually these  valley  systems  were  extended  as  well  as  deepened,  until  today 
the  region  is  an  upland  of  rolling  prairie,  a  great  sea  of  hills  and  valleys 
Avith  smooth  flowing  outlines.  The  hill  tops  rise  to  nearly  the  same 
level,  and  the  main  divides  or  ridges  between  the  valley  systems  are 
remarkably  flat  topped,  representing  the  remnants  of  a  once  continuous 
penqplain.  Here  and  there  a  liigher  knob  or  ''mound"  rises  the  upland 
level,  a  residual  hill  which  escaped  base-leveling.  But,  for  the  most 
part,  the  relief  is  one  of  monotonous  regularity.  I^ong  continued  decay 
of  the  rock?  has  produced  a  residual  soil  several  feet  thick,  which  passes 
downwards  by  unbroken  transition  into  the  firm  unweathered  rock. 

The  pre-glacial  topography. — A  surface  similar  to  that  of  the  drift- 
less area  was  developed  before  the  glacial  period  in  northeastern  Illinois. 
At  the  same  fimo.  it  is  altogothor  probable  that  a  broad  lowland  had 


GOLDTHWAiT.]  SURFACE   OF   BED    ROCK.  ^O 

• 

been  developed  where  Lake  Michigan  now  lies,  for  the  rock  formations 
which  underlie  the  lake  are  a  series  of  soft  Devonian  shales  and  sand- 
stones which  would  be  reduced  much  faster  than  the  hard  Niagara 
limestones  farther  west.  Possibly  also,  there  was  a  somewhat  distinct 
escarpment  running  from  north  to  south  in  the  western  part  of  our  dis- 
trict, owing  to  the  greater  reduction  of  the  Cincinnati  shales,  which  lie 
west  of  the  Niagara  limestones.  The  hills  carved  out  of  the  hard  lime- 
stones at  Joliet  may  have  descended  rather  abruptly  a  few  miles  west  of 
the  city  to  a  lower,  flatter  district  occupied  by  the  shales. 

The  development  of  underground  drainage. — The  limestone  of  this 
region  not  only  suffered  decay  and  erosion  at  the  surface,  but  was  at- 
tacked by  ground  water.  Any  rock  structure  so  extensively  affected 
by  joints  permits  water  to  work  its  way  downward  at  a  rather  rapid  rate. 
This  water,  charged  with  a  small  amount  of  certain  acids,  the  carbon 
dioxide  from  the  air,  the  humus  acids  from  the  soil,  can  slowly  dissolve 
certain  rock  constituents,  especially  limestone,  which  is  very  largely 
composed  of  soluble  lime  carbonate.  Thus  it  comes  about  that  material 
is  dissolved  from  the  two  faces  of  every  joint  crack  in  limestone,  and  the 
joint  is  slowly  enlarged.  Under  favorable  conditions  definite  under- 
ground stream  channels  may  be  eaten  out  in  time.  These  may  grow 
into  large  passages  and  caverns.  It  is  in  fact  in  just  this  way  that  the 
great  limestone  caverns  of  Indiana,  Kentucky  and  Virginia  were  made. 
If  a  cavern  is  not  far  underground  and  is  so  greatly  enlarged  that  i\\^ 
roof  falls  in,  a  '"sink"'  or  '"'sink  hole"'  results.  These  sink  holes  are  saucer 
shaped  depressions  in  the  ground.  While  in  some  cases  they  originate 
after  the  fashion  just  described,  it  is  probable  that  most  sink  holes  are 
developed  by  local  enlargement  of  innumerable  small  passageways 
through  which  water  drains  downward  from  the  surface,  and  without 
the  development  of  any  great  cavern  immediately  beneath.  Surface 
drainage  flowing  into  sinks  increases  their  size,  and  eventually  almost 
the  whole  drainage  of  a  district  mav  enter  sinks  and  follow  underground 
channels.    This  condition  has  been  reached  in  the  interior  of  Florida. 

While  no  such  wholesale  development  of  sinks  and  subterranean 
streams  occurred  in  northern  Illinois  before  the  ice  age,  sinks  are  known 
to  exist  there,  in  spite  of  the  fact  that  the  drift  so  generallv  conceals 
them.  Two  or  three  good  sized  hollows,  leading  to  caves  of  unknown 
extent,  could  formerly  be  seen  in  the  west  part  of  Joliet,  near  Jasper 
street  and  Eaynor  boulevard.  They  have  been  more  or  less  filled  up  with 
rubbish  in  recent  years,  so  that  they  cannot  satisfactorily  be  examined. 
In  places,  small  tunnels  or  openings  in  the  limestone  may  be  seen  in  the 
quarries  about  Joliet,  though  none  of  them  are  of  striking  proportions. 
One  appears  in  the  northeast  corner  of  the  quarry  near  Grinton  and 
Jackson  streets.  It  is  a  thin  horizontal  opening  worked  out  along  a 
bedding  plane  in  the  limestone,  close  to  the  present  quarry  floor.  The 
steady  flow  of  water  through  these  openings  renders  them  most  unwel- 
come to  the  quarrymen,  necessitating  the  constant  use  of  pum23s.     It  is 


2<) 


THE   DES  PLAINES   VALLEY. 


Lbuli,.  no.  U 


said  that  a  Pi)riiig  issuing  from  tlic  limestone  near  here,  was  formerly 
a  regular  stopping  place  for  the  stage,  as  it  passed  down  the  Des  Plaines 


valk'V  through  Jolict, 


GLACIATION. 


The  Glacial  Period. — The  rolling  upland  with  its  maturely  developed 
valley  systems  and  its  residual  soil  was  destined  not  to  remain.  An 
extraordinary  change  of  climate  led  to  the  development  of  a  great  ice 
field  over  much  of  the  northern  part  of  North  America.     The  extent  of 


Fig.  5.  Map  of  area  covered  by  the  North  American  ice  sheet  of  the  glacial 
epoch  at  its  maximum  extension,  showing  the  approximate  soutliern  limit  of  glaci- 
ation,  the  three  main  centers  of  Ice  accumulation,  and  the  driftless  area  within  the 
border  of  the  glaciated  region.      {Courtesy  of   U.   8.   Geological  Survey.) 

the  ice  sheet  (shown  in  Fig.  5)  was  some  4,000,000  square  miles,  fully 
the  size  of  the  ice  sheet  which  now  covers  the  Antartic  continent.  Why 
such  an  enormous  ice  sheet  grew  up  in  North  America,  with  its  centers 
of  accumulation  nearly  thirty-five  degrees  away  from  the  pole,  has 
never  been  satisfactorily  explained.     It  has  been  ascribed,  in  turn,  to 


GOLDTHWAIT.]  SURFACE   OF    BED    ROCK.  27 

a  general  uplifting  of  the  continent  to  an  altitude  above  the  snow  line; 
to  a  shifting  of  ocean  currents  by  up-warpings  of  the  sea  floor ;  to  certain 
changes  in  the  earth's  planetary  relations  (eccentricity  of  the  orbit  and 
precession  of  the  equinoxes)  which  might  rarely  combine  to  give  a  series 
of  ice  caps,  alternately  at  the  north  and  south  pole;  to  a  shifting  of  the 
poles  themselves,  with  respect  to  the  crust  or  outer  shell  of  the  earth ; 
and  to  changes  in  constitution  of  the  atmosphere,  wherein  slight  en- 
richment in  carbon  dioxide  gas,  accomplished  by  certain  geologic  and 
geographic  changes,  might  bring  about  a  cool  moist  climate.  All  these 
except  the  last  have  met  serious  objection,  and  while  this  cannot  be 
said  to  have  been  demonstrated  it  seems  the  most  satisfactory  yet  sug- 
gested. 

The  JSTorth  American  ice  sheet,  as  the  map  (Fig.  5)  indicates,  probably 
extended  as  far  north  as  the  continent  itself.  Greenland  is  believed  to 
have  been  covered  by  its  own  separate  ice  cap.  A  similar  ice  sheet,  with 
its  center  on  the  Scandinavian  peninsula,  covered  all  of  northwestern 
Europe  and  most  of  the  British  Isles.  On  the  Alps  there  was  a  smaller, 
isolated  ice  field,  from  which  great  tongues  of  ice  moved  down  the  main 
ralleys. 

It  must  not  be  thought,  however,  that  the  North  American  ice  sheet 
was  a  group  of  narrow  glaciers  moving  out  from  an  elevated  mountainous 
center.  While  the  Canadian  highlands,  from  which  it  spread,  stand 
somewhat  above  the  general  level  of  the  upper  Mississippi  valley,  the 
motion  of  the  ice  was  not  controlled  by  the  topography.  Rather  was 
it  a  vast  sheet,  radiating  out  from  three  (possibly  four)  centers,  with  the 
ice  from  at  least  two  of  them  coalescing  to  form  a  single  great  ice  cap. 
The  ice  in  the  western  mountains  appears  to  have  remained  measurably 
distinct. 

The  history  of  the  glacial  period  Avas  complex.  It  was  made  up 
of  several  glacial  and  interglacial  epochs.  In  the  former  the  ice  sheets 
grew  larger ;  in  the  latter  they  dwindled,  or  disappeared  altogether.  The 
glacial  epochs  evidently  represent  periods  of  severer  climate,  while  the 
interglacial  epochs  mark  times  of  milder  climate.  The  glacial  period 
was  therefore  a  period  of  climatic  changes.  We  seem  now  to  be  living 
in  a  post-glacial  epoch,  but  if  another  glacial  epoch  should  follow,  the 
present  would  prove  to  have  been  an  interglacial  epoch.  It  may  be  said, 
in  this  connection,  that  some  of  the  interglacial  epochs  seem  to  have  been 
much  longer  than  the  time  since  the  ice  last  withdrew. 

The  ice  sheet  was  thick  enough  to  cover  the  hill  tops  everywhere  with- 
in reach,  and  even  to  bury  the  mountains  of  northern  New  York  and  of 
New  England.  We  may  get  some  idea  of  its  thickness  over  the  Des 
Plaines  basin  by  measuring  the  distances  out  to  the  border  of  the 
glaciated  area  and  assuming  a  surface  slope  in  this  distance,  equal  to 
that  of  the  Greenland  ice  cap.  When  the  ice  had  its  greatest  extent  in 
Illinois  (in  the  "Illinoian"  epoch)  its  outer  edge  was  more  than  300 
miles  south  of  the  Des  Plaines  district  (see  Fig.  6).  If  the  average 
slope  of  its  surface  at  that  time  was  thirty  feet  per  mile,  i.  e.,  about  the 
same  as  that  of  the  interior  oi;  the  Greenland  glacier,  the  thickness  jf 


28 


THE    DES  PLAINES    VALLEY. 


[BUI.T. .    NO.    11 


ice  over  the  Dos  Plaines  basin  was  some  9,000  feet.  It  seonis  unlikely, 
liowever,  that  such  a  steep  slope  as  that  would  continue  so  far  from  the 
ice  maririn.  Nansen,  in  his  trip  across  Greenlanrl,  found  that  on  the  west 
side  (where  the  slope  was  gentler  than  on  the  east)  the  surface  of  the 
ice  cap  rose  to  6,600  feet  in  the  first  seventy-six  miles,  and  after  that  at 


Fio.   6.     Moraines  and   other  limit   of  drift   in   Illinois.     After  Leverett.   U. 
Geol.   Surv.) 


GOLDTHWAIT.J  -  SURFACE   OF    BED    ROCK.  29 

an  average  rate  (constantly  decreasing)  of  twenty-six  feet  per  mile. 
If  we  assume  the  same  rate  for  Illinois,  we  get  6,600  feet  for  the  first 
seventy-six  miles  back  from  the  ice  border,  and  5,850  feet  for  the  225, 
miles  following,  or  a  total  thickness  over  Joliet  and  Chicago  of  over 
12,000  feet.  There  is  reason  to  believe,  however,  that  the  Greenland 
ice  sheet  covers  a  high  mountainous  region  from  which  there  is  a  rather 
steep  descent  to  the  sea;  and  that  the  slope  of  the  surface  of  the  ice 
sheet  is  steeper  on  that  account  than  it  would  be  over  a  flat  region  like 
Illinois.  So  far  as  this  is  true  it  should  lead  us  to  reduce  the  estimate 
of  thickness  accordingly.  We  may  reasonably  believe,  however,  that 
during  the  Illinoian  ice  invasion  the  ice  sheet  was  several  thousand 
feet  thick  over  northeastern  Illinois.  During  the  last  glacial  epoch,  how- 
ever, the  ice  advanced  only  a  short  distance  southwest  of  the  Des  Plaines 
valley,  and  its  thickness  over  that  area  was  probably  not  more  than  a  very 
few  thousand  feet. 

For  a  long  period,  probably  a  hundred  thousand  years,  this  great  cap 
of  ice  was  a  powerful  agency  in  modifying  and  reshaping  the  surface 
features  of  this  district.     When  it  finally  melted  away,  on  the  establish- 

(a)  ■     lb) 

Cot  ,;f 


J \ i L_ 

Fig.   7.     Section  showing    (a)    residual   soil,   passing  downward  into   rock,   and 
(b)   glacial  drift  overlying  a  glaciated  rock  surface  unconformably. 

ment  of  the  present  climate,  a  wholly  new  topography  appeared.  In 
two  distinct  ways  the  ice  sheet  had  changed  the  topography  of  the  sur- 
face. It  had  carried  away  the  residual  soils  and  most  of  the  loose  rock 
within  the  zone  of  surface  decay  and  disintegration,  and  as  a  rule  it 
ground,  scraped,  and  scoured  the  firm  rock  below  until  its  surface  was 
reduced,  in  manv  places  at  least,  several  feet  below  its  former  position 
(See  Fig.  7). 

The  smoothing  and  striating  of  the  roclc  surface. — The  appearance  of 
a  strongly  glaciated  surface  of  rock  is  so  characteristic  that  it  deserves 
more  than  mention.  The  drift-shod  ice,  moving  slowly  along  over  the 
rock  floor  and  pressing  down  upon  it  with  tremendous  weight,  rasps 


30  THE   DES  PLAINES   VALLEY.  [bull.  no.  li 

and  scours  it.  The  finely  comminuted  clay  or  ''rock  flour"  which  makes 
up  a  large  part  of  the  drift,  probably  lubricated  with  water,  smooths 
and  even  polishes  the  rock  surface.  Coarser  particles  in  the  ice  such  as 
sharp  cornered  bits  of  rock,  are  held  firmly  against  the  bed  rock  like  en- 
graving tools,  scratching  the  surface  more  or  less  deeply  in  the  direction 
of  glacier  motion,  until  the  cutting  edge  is  blunted  or  the  pebble  turns 
around.  Tiicse  scratches  or  "strije,"  where  best  formed  (on  rock  of  fine 
grain,  dense  texture,  but  of  relatively  slight  hardness,  like  certain  layers 
of  the  Niagara  limestone)  begin  abruptly  and  gradually  narrow  or  tail 
out  in  the  direction  in  which  the  glacier  advanced.  They  vary  in  size 
from  scratches  of  a  hair's  breadth  to  grooves  several  inches  in  cross  sec- 
tion. Large  bowlders  were  probably  the  carving'  tools  in  the  case  of 
the  larger  grooves.  In  length  the  fine  scratches  are  to  be  measured  by 
inches  rather  than  feet.  With  a  little  practice,  striae  can  be  distinguished 
readily  from  cracks.  The  scratches  are  mere  surface  markings,  and 
can  be  seen  only  on  well  smoothed  surfaces  of  freshly  exposed  rock. 
Cracks,  of  course  penetrate  the  rock  and  may  occur  on  any  surface.  As 
a  rule  the  scratches  at  a  given  point  follow  a  single  direction,  which  is 
that  of  ice  motion  when  the  rock  surface  was  last  covered  by  ice.  Oc- 
casionally, however,  two  or  more  sets  of  scratches  cross  one  another,  testi- 
fying to  the  local  shifting  of  the  direction  of  ice  movement. 

Striated  rock  surfaces  are  to  be  looked  for  where  the  drift  has  been 
only  recently  stripped  away,  as  around  the  borders  of  freshly  worked 
quarries.  Where  a  rock  surface  has  been  exposed  even  for  a  few  years 
the  decay  of  the  limestone  has  usually  obliterated  them.  Moreover  no 
striae  are  likely  to  remain  where  the  rock  surface  was  washed  by  streams 
during  the  retirement  of  the  ice  sheet,  and  was  buried  by  gravels.  For 
these  reasons  chiefly,  striated  surfaces  are  rarely  seen  near  Joliet.  The 
rock  floor  of  the  valley  was  cut  down  by  an  ancient  river  (the  outlet 
of  extinct  Lake  Chicago)  and  the  rock  up  to  the  height  of  some  fifty 
feet  on  either  side  of  the  valley  was  washed  by  gravel-bearing  streams. 
A  smoothed  rock  surface  has  been  recently  exposed  beside  the  track  of 
the  Coal  City  branch  of  the  Chicago  &  Alton  railway,  just  southeast  of 
the  switch  house  on  South  Chicago  street.  No  scratches  can  be  seen  on 
it,  however,  and  the  gravelly  and  bouldery  drift  which  has  been  stripped 
away  seems  to  indicate  that  the  surface,  if  ever  scratched  by  the  ice,  was 
subsequently  eroded  by  running  water. 

The  hiirml  of  the  rock  surface  with  drift. — Over  the  glaciated  surface 
of  the  bed  rock  the  glacier  spread  a  sheet  of  rock  debris  or  "drift." 
which  it  had  collected  on  its  way  southward,  and  which  it  was  unable 
to  carry  farther  out  to  the  position  of  its  extreme  border  in  southern 
Illinois.  So  the  residual  soils  of  pre-glacial  time  were  taken  off,  the 
underlying  rock  worn  down  to  some  extent,  and  then  buried  by  a  sheet 
of  drift  of  variable  thickness.  The  contact  of  the  rock  and  the  drift  is 
therefore  a  true  "unconformity."  the  record  of  an  interval  of  erosion 
between  two  widely  separated  periods  of  deposition.  Too  much  emphasis 
can  not  be  placed  on  this  feature,  so  characteristic  of  the  glaciated  region. 


GOLDTHVVAIT.]  SURFACE   OF   BED    EOCK.  31 

The  buried  topography. — The  rolling  upland  of  pre-glacial  time  was 
probably  modified  only  slightly  by  glacial  erosion.  There  is  no  evidence 
that  any  profound  erosion  took  place.  The  pre-glacial  valleys  were 
probably  somewhat  deepened  and  widened,  and  the-  hill  tops  were  some- 
what reduced,  but  the  undulatory  character  of  the  bed  rock  surface  re- 
mained, with  probably  little  change  in  the  amount  of  unevenness.  This 
fact  is  suggested  by  data  from  wells  and  by  the  exposures  in  quarries, 
and  along  the  vallevs  where  the  drift  has  been  removed.  Take,  for  ex- 
ample,  the  profile  of  rock  along  the  Des  Plaines  valley  from  Lemont  to 
Willow  Springs.  At  Lemont  the  Niagara  limestone  appears  on  either 
side  of  the  valley  in  the  bluffs,  to  a  height  of  about  fifty  feet  above  the 
valley  floor,  or  sixty  feet  above  Lake  Michigan.  As  exposed  in  the  wall 
of  the  quarry  west  of  the  village  the  surface  of  the  rock  declines  grad- 
ually to  the  level  of  the  valley  floor  in  two  miles.  East  of  Lemont,  like- 
wise, the  surface  of  the  bed  rock  descends,  reaching  the  level  of  the  river 
within  a  mile  and  a  half.  Opposite  the  mouth  of  the  "Sag"  the  bed 
rock  (by  measurements  along  the  drainage  canal)  ranges  from  fifteen 
to  thirty-five  feet  below  the  valley  floor,  or  five  to  twenty-five  feet  below 
Lake  Michigan,  indicating  a  change  of  altitude  of  the  rock  surface  of" 
eighty-five  feet  between  the  highest  point,  at  Lemont,  and  the  lowest, 
near  Sag  bridge.  That  the  bed  rock  surface  rises  and  falls  as  much  as 
eighty-five  feet,  even,  in  comparatively  short  distances  is  indicated  by 
the  presence  of  a  rock  outcrop  on  Saw  Mill  creek,  about  a  mile  north- 
west of  Sag  bridge,  and  at  a  height  of  nearly  seventy-five  feet  above 
Lake  Michigan.  This  means  for  that  vicinity  at  least  a  vertical  range 
of  100  feet  in  a  mile.  It  is  not  likely  that  these  measurements  (the 
highest  and  the  lowest)  are  extreme;  rather  does  it  appear  that  the 
rock  surface  rises  and  falls  with  moderate  slopes  in  innumerable  hills 
and  valleys  of  about  the  size  and  height  of  the  morainic  hills  on  Mt. 
Forest  island. 

In  places  the  surface  of  the  bed  rock  after  glaciation  had  really  pre- 
cipitous slopes.  Such  was  the  case,  apparentl}^,  near  Lemont,  where  sharp 
rock  bluffs  overlook  the  valley  floor.  At  first  sight  these  bluffs  might  be 
thought  to  be  the  work  of  the  Des  Plaines  river  or  its  ancestor,  the  outlet 
of  glacial  Lake  Chicago,  which  once  poured  through  the  valley,  and  which 
might  easily  have  cut  a  deep  notch  through  the  bed  rock  had  there  been 
a  rock  barrier  athwart  its  course  at  Lemont.  Such  an  explanation  for 
the  bluffs  and  the  rocky  floor  of  the  valley  has  in  fact  been  entertained. 

The  contrary  belief,  i.  e.,  that  the  valley,  with  its  rocky  floor  and  sides, 
was  already  in  existence  when  the  ice  sheet  last  covered  the  district,  and 
that  no  rock  barrier  crossed  the  Chicago  outlet  at  Lemont,  is  based  on 
the  distinctly  glaciated  character  of  the  bed-rock  floor  of  the  valley  at 
several  points  between  the  opposed  bluffs.  At  the  quarries  on  the  north 
side  of  the  valley  about  Lemont,  near  where  the  Santa  Fe  railway  turns 
obliquely  across  the  river  and  the  drainage  canal,  the  bed  rock  floor  of 
the  valley  at  the  base  of  the  bluffs  is  smoothed  and  polished  and  distinctly 
scratched.  The  striae  run  about  south  50°  west,  parallel  to  the  axis 
of  the  valley.  The  best  exposure  noted  is  at  the  northeast  end  of  the 
quarries,  where  a  thin  covering  of  glacial  drift  in  April,  1907,  had  just 


ip 


32        *  THE   DES  PLAIN5S   VALLEY.  [bull.  no.  11 

bue'ii  stripped  I'luiu  tlio  ruc-k  iloor.  Clearly  this  s})ot  in  the  valley,  at 
least,  was  ouce  scoured  by  the  glacier.  Similar  exposures  a  few  hundred 
yards  away  conllrm  this  \iew.  and  suggest  that  the  whole  valley  was 
once  fdlcd  and  buried  by  glacier  ice.  Such  glacial  markings  on  the 
valley  floor  have  been  noted  before  at  Lemont.  A  strongly  glaciated 
surface,,  exposed  in  the  bed  of  the  Chicago  drainage  canal  at  this  place, 
was  described  and  pictured  by  Leverett  in  his  monograph  on  "The  Illi- 
nois Glacial  Lobe.*"^  It  is,  of  course,  not  safe  to  insist  that  no  rock  bar- 
rier could  have  crossed  the  valley  somewhere  just  above  or  below  Lemont, 
until  it  is  known  that  the  floor  of  the  vallev  shows  marks  of  glaciation 
as  far  down-stream  as  it  is  bordered  by  rock  bluffs — a  matter  as  yet 
undetermined.  But  the  evidence  just  reviewed  strongly  favors  that  view. 
The  valley  at  Lemont  seems  to  be  a  glaciated  valley,  and  not  a  post-glacial 
valley  of  river  excavation.  Besides  throwing  light  on  this  question  of 
a  rock  barrier  at  Lemont,  the  striated  surfaces  at  the  base  of  the  bluffs 
illustrate  the  local  steepness  of  bed-rock  slopes  which  were  covered  and 
scrubbed  by  the  ice. 

'U.  S.  Geol.  Surv.,  Monograph  38,  p.  416. 


GOLDTHWAIT]         GLACIAL    AND    INTER-GLACIAL    DEPOSITS.  B3 


CHAPTER  IV. 


THE  GLACIAL  AXD  INTER-GLACIAL  DEPOSITS. 

The  nature  and  history  of  the  extinct  North  American  ice  sheet  has 
been  outlined  in  the  preceding  chapter.  The  manner  in  which  it  eroded 
the  surface  of  the  underljdng  rock  has  also  been  briefly  told.  We  have 
now  to  consider  in  some  detail  the  deposits  which  the  ice  left  on  its 
retreat,  and  those  laid  down  in  inter-glacial  periods.  To  the  deposits  of 
glacial  drift  we  owe  all  the  main  features  of  the  present  topography  and 
indeed  most  of  the  details  of  the  surface. 

DISTEIBUTION  AND  SURFACE  FORil  OF  THE  DRIFT. 

The  map  of  the  Des  Plaines  district  (Plate  1)  and  an  introductory 
sketch  of  the  leading  features  of  relief  on  pages  3  and  4  indicate  the 
massing  of  the  drift  into  parallel  belts  of  upland,  known  as  terminal 
moraines.  Each  of  these  moraines  marks  a  stage  in  the  recession  of  the 
ice  border,  when  the  rate  of  melting  was  temporarily  checked  and  the. 
edge  of  the  ice  became  nearly  stationary.  At  such  times  the  drift  which 
was  being  moved  forward  to  the  melting  border  and  deposited  there, 
accumulated  to  great  thickness.  When  the  ice  border  receded  a  relatively 
smooth  lowland  was  laid  bare  behind  the  belt  of  thick  drift.  This  ex- 
tended to  the  time  when  another  halt  of  the  ice  caused  the  making  of 
another  ridge  of  drift. 

It  is  characteristic  of  these  terminal  moraines  to  have  a. very  uneven 
surface.  The  uneveunesses  consist  of  depressions  and  swells,  more  or'  less 
like  upriglit  and  inverted  saucers,  yet  too  irregular  in  outline  to  be  de- 
scribed accurately  in  those  terms.  The  range  of  undulation  and  the 
angle  of  slope  vary  in  the  different  moraines.  They  are  greatest  on  the 
largest  one,  the  Valparaiso  moraine,  reaching  on  Mt.  Forest  Island  a 
relief  of  over  fifty  feet  between^ hill  top  and  valley  bottom.  At  Hinsdale 
the  relief  is  somewhat  less  marked,  with  a  range  of  about  thirty  feet, 
and  around  Elmhurst  the  eastern  portion  of  the  moraine  has  very  wide 
flatfish  sags  and  swells.  On  the  smaller  moraines,  the  Minooka  till  ridge, 
the  west  ridge  of  the  Valparaiso  morainic  system  north  of  Joliet.  and  the 
lake  border  moraines,  the  undulations  of  the  surface  are  very  faint  com- 
prising long  gentle  slopes  which  rise  and  fall  no  more  than  fifteen  to 
twentv  feet  in  long  distances.     The  size  of  the  hills  is  also  variable. 

-8  G 


34  THE   DES   PLAINES  VALLEY.  [bull.  no.  11 

They  are  commonly  half  a  mile  to  a  mile  in  longest  diameter.  The 
liollows  are  oi'ten  enclosed  basins,  in  which  surface  water  collects  to  form 
swamps  or  little  ponds  in  wet  weather.  This  is  favored  by  the  im- 
permeability of  the  compact  clay  of  which  moraines  are  largely  composed. 
There  seems  to  be  little  regularity  in  the  trend  of  swells  and  sags,  for  in 
some  places  they  appear  to  run  roughly  parallel  to  the;  former  border  of 
the  ice  and  in  other  places  they  are  prevailingly  perpendicular  to  it. 

Tiie  cause  of  the  marked  irregularity  of  the  surface  of  moraines  is 
to  be  found  in  the  variability  of  conditions  under  which  the  moraines 
^rew  up.  In  the  first  place,  the  drift  was  not  evenly  scattered  through 
the  ice,  so  that  much  more  reached  the  melting  border  of  the  ice  at  some 
points  than  at  others.  Low  mounds  and  hollows  on  the  surface  of  the 
<leposit  naturally  resulted.  Secondly,  the  ice  edge  was  oscillating  back- 
Avard  and  forward  locally  at  dillcrent  rates,  so  that  the  drift  was  spread 
out  more  in  some  places  than  in  others,  and  deposits  once  made  were 
frequently  overridden  by  local  re-advances  of  the  ice.  In  some  cases, 
moreover,  blocks  of  ice  were  left  behind  as  the. ice  retreated.  If  these 
were  surrounded  or  buried  with  gravel  their  melting  may  have  led  to 
the  formation  of  hollows  in  the  surface  of  the  drift. 

The  deposit  left  beneath  the  ice.  between  the  morainic  ridges,  is 
known  as  the  "ground  moraine."  This  too  has  its  swells  and  hollows, 
but  in  this  region  they  are  much  less  pronounced  than  those  of  the 
terminal  moraines.  The  belts  of  ground  moraine  have  the  appearance  of 
rather  smooth  plains.  The  broad  shallow  valley  followed  by  the  upper 
Des  Plaines  river,  above  Kiverside,  is  one  of  these  plains.  Its  lower 
portion,  as  well  as  the  adjoining  Chicago  plain,  was  afterwards  covered 
by  the  glacial  Lake  Chicago,  and  the  initial  smoothness  was  increased 
by  the  leveling  action  of  waves  and  currents,  which  tended  to  cut  down 
the  elevations  and  to  build  up  the  depressions.  The  lake  plain  in  many 
places  appears  to  be  absolutely  flat  for  miles.  This  is  its  appearance 
at  the  city  limits  of  Chicago,  near  Archer  avenue,  and  west  of  Harlem, 
around  "Broadview." 

THICKNESS  OF  THE  DRIFT. 

The  undulating  surface  of  the  bed  rock,  and  the  equally  irregular 
surface  of  the  drift,  with  no  correspondence  in  position  between  the  two, 
combine  to  give  the- drift  a  very  irregular  thickness.  Local! v,  as  already 
remarked,  the  drift  is  almost  or  quite  absent.  There  are  other  places 
where  well  borings  show  it  to  be  more  than  200  feet  thick.  As  a  rule, 
however,  in  the  neighborhood  of  the  Valparaiso  moraine,  where  we  may 
expect  the  maximum  thickness  for  the  Des  Plaines  valley  district,  it  is 
100  to  l.")0  feet  thick.  At  five  localities  in  our  district  well  records  col- 
lected by  T;everett^  show  thicknesses  as  follows: 

Arlington  Heights  (about  150  feet  below  crest  of  moraine) 128 

North  of  Arlington  Heights  (20  to  30  feet  above  station) ['.  190 

Elmhurst     '      no 

Crest  of  moraine  northwest  of  Lemont 150 

Crest  of  moraine  east  of  Lockport 115+ 


l"The  Illinois  Glacial  Lobe."     U.  S.  Geo).  Surv.,  Monograph  3S,  p.  3.54.  1S99. 


GOLDTHWAITJ         GLACIAL    AND    INTER-GLACIAL    DEPOSITS.  bo 

This  gives  an  average  of  136  feet  along  the  axis  of  the  moraine.  The 
greatest  thickness  in  the  table  is  by  no  means  a  maximum,  but  it  is  not 
likely  that  the  drift  is  much  over  350  feet  thick  anywhere  in  the  Des 
Plaines  basin,  since  out  of  68  well  records  cited  by  Leverett  on  the  Val- 
paraiso moraine  between  northern  Illinois  and  southwestern  Michigan, 
only  four  are  certainly  over  250  feet,  and  only  one  is  over  300  feet.  The 
deepest  visible  section  through  the  drift  in  our  district  is  two  or  three 
miles  west  of  Lemont,  where  the  broad  valley  crosses  the  axis  of  the 
great  Valparaiso  moraine,  and  the  extensive  stripping  of  the  rock  in  the 
bluff  on  the  south  side  of  the  valley  has  freshlv  exposed  the  drift  to  a 
depth  of  some  75  feet. 

COMPLEXITY  OF  THE  DRIFT. 

Because  of  the  complexity  of  the  ice  age,  the  series  of  advances  and 
retreats  of  the  ice,  the  drift  does  not  consist  merely  of  a  single  sheet, 
but  of  several  overlapping  sheets,  deposited  by  the  successive  glaciers.- 
It  is  through  the  study  of  these  several  drift  sheets  that  investigators 
of  glacial  geology,  during  the  past  twenty-five  years  have  worked  out 
the  fact  of  successive  glaciations.  In  Illinois  and  the  adjoining  states, 
the  later  ice  advances  as  a  rule  fell  short  of  the  earlier,  so  that  each  of 
the  five  drift  sheets  is  to  be  found  locally  as  a  surface  deposit  south 
of  the  outer  border  of  the  next  younger  sheet.  Even  where  an  earlier 
sheet  was  run  over  by  a  later  advance  of  the  ice,  the  old  drift,  buried 
beneath  the  later  drift  sheet,  may  sometimes  be  found  where  streams  have 
excavated  valleys  through  the  deposits,  or  some  other  section,  natural  or 
artificial,  has  been  made.  An  older  drift  sheet  is  often  separated  from 
a  younger  one  above  either  by  an  old  surface  with  its  evidences  of  erosion, 
soil  decay,  and  vegetation  (in  the  form  of  peat  beds,  tree  trunks,  etc.), 
or  by  stratified  deposits  of  sand  and  gravel  which  indicate  deposition 
by  rivers  or  lakes  during  the  inter-glacial  epoch.  Often,  however,  the 
older  drift  sheet  was  wholly  destroyed  before  the  deposition  of  the  newer 
drift,  either  by  surface  erosion  or  by  the  later  ice  advance.  Conse- 
quently one  rarely  finds  in  any  single  exposure  more  than  two  or  three 
glacial  and  inter-glacial  deposits,  and  in  most  cases  there  is  only  the  last 
drift  sheet  over  the  bed  rock.  The  five  drift  sheets  recognized  in  the 
upper  Mississippi  valley  as  marking  five  distinct  advances  of  the  ice  have 
been  named  in  the  order  of  their  age  (1)  sub-Aftonian,  or  Jerseyan, 
(3)  Kansan,  (3)  Illinoian,  (4)  lowan,  (5)  Wisconsin.  The  last  has  in 
turn  been  subdivided  into  the  early  and  the  late  Wisconsin  stages. 

THE  TWO   KINDS   OF   DRIFT. 

The  fragmental  rock  material  which  was  transported  by  the  ice  sheet 
and  sooner  or  later  deposited  in  a  new  locality  is  known  as  the  "drift." 
The  greater  part  of  it  was  deposited  directly  by  the  ice.  This  is  known 
as  "till."  But  much  of  the  drift  was  worked  over  hj  running  water  as 
the  ice  sheet  melted  away,  and  was  laid  down  in  beds  or  strata.  This  is 
known  as  "stratified  drift."     It  resembles  till  in  one  respect,  in  being 


36  THE   DES  PLAINES   VALLEY.  [bull.  no.  It 

cninposed  of  fragments  of  rocks  of  very  many  different  sorts;  but  it 
dillVrs  from  till  very  markedly  in  ^jhysieal  structure,  possessing  stratifi- 
cation, which  is  unknown  in  ice-laid  drift.  The  distinction  is  a  funda- 
mental one,  and  will  be  emphasized  in  the  fgllowing  discussion  of  the 
till  and  of  the  stratified  drift. 

Tlie  ice-laid  drift  or  "till". — The  most  striking  character  of  the  till 
is  the  great  range  in  size  of  the  fragments  which  compose  it,  and  the 
entire  absence  of  separation  of  coarse  from  fine.  Large  bowlders,  cob- 
bles, pebble?,  sand,  clay,  and  the  finest  "rock  flour"  are  mingled  in  ab- 
solute confusion.  This  arises  from  the  fact  that  a  glacier  has  great  power 
as  a  transporting  agency ;  tlie  heaviest  bowlder  can  be  carried  on  its  sur- 
face or  within  its  frozen  mass  almost  as  easily  as  a  particle  of  clay. 
AVhere  the  strength  of  the  ice  movement  is  locally  diminished,  deposi- 
tion all'ects  coarse  and  fine  alike.  There  results  a  heterogeneous  mixture 
known  sometimes  as  "bowlder  clay"  (synonymous  with  "till".)  Xot  so 
with  deposits  which  are  laid  down  by  running  water  or  by  wind.  These 
two  agencies  are  very  limited  in  their  carrying  power.  Each  variation 
in  the  strength  of  a  current  of  water  means  a  variation  in  the  size  of 
the  particles  which  it  may  carry  or  deposit.  Accordingly,  at  one  time 
fine  sand  may  be  deposited,  and  later,  if  the  current  becomes  stronger, 
eoar,«e  sand  or  gravel  may  be  deposited  at  the  same  place.  "With  wind  a 
similar  change  leads  to  successive  layers  or  beds  in  the  deposit,  although 
wind  is  of  course  not  strong' enough  to  transport  gravel.  Ice-laid  de- 
posits, then,  are  peculiar  in  their  absence  of  stratification. 

Another  criterion  of  ice  deposits  is  the  shape  of  the  stony  ingredient. 
Although  many  of  the  bits  of  rock  in  bowlder  clay  are  rounded  like  river 
or  beach  pebbles  (and  it  is  significant  in  this  connection  that  the  diabase 
and  granite  pebbles  and  bowlders  Avhich  have  come  far  are  usually 
rounder  than  the  limestone  fragments  of  local  derivation)  a  large  num- 
ber arc  angular  or  suli-angular,  with  snubbed  ends,  rounded  edges,  and 
smoothed  and  striated  sides.  (See  Plate  3,  Xo.  2).  The  striae  resemble 
those  of  a  glaciated  bed  rock  surface,  and  are  made  in  just  the  same  way, 
only  the  stones  of  the  drift  are  in  motion,  and  scratch  against  one  another 
as  well  as  against  the  bed  rock.  If  a  stone  in  the  till  is  decidedly  longer 
in  one  direction  than  in  others,  its  striae  as  a  rule  run  parallel  to  its 
length,  because  the  stone  tends  to  orient  itself  in  the  position  in  which  it 
will  offer  least  resistance  to  the  abrading  force.  This  feature  is  illus- 
trated in  the  glacial  stone  in  Plate  3. 

As  regards  the  composition  of  its  rock  particles,  the  till  exhibits  a 
very  remarkal)le  variety.  The  pebbles  and  bowlders  show  a  lithological 
heterogeneity  far  greater  than  any  lot  of  pebbles  that  a  river  or  a  lake 
alone  would  be  likely  to  collect.  While  most  of  the  pebbles  resemble  the 
underlying  rock,  many  of  them  correspond  to  rock  formations  which 
occur  not  nearer  than  50.  100,  or  even  several  hundred  miles.  Such,  for 
instance,  are  the  granites,  diabases,  quartz-porphyries  and  amvgdaloids, 
which  came  from  northern  Wisconsin  or  beyond,  and  the  quartzites  which 
came  from  the  same  region  or  perhaps  from  certain  >small  area?  of  • 
quartzite  in  south  central  Wisconsin.  Xo  agency  except  ice  is  known, 
by  which  rock  material  would  be  collected  from  such  Avidely  separated 


STATE  GEOLOGICAL,  SURVEY. 


BULL.   NO.    11,    PL.    3. 


Pebbles    from    the    drift.       (1)    glacial    gravel,    (2)    till,    (3)    gravel    pebbles    partly 

cemented    by    carbonate    of   lime. 


GOLDTHWAIT.J         GLACIAL    AND    INTEE-GLACIAL    DEPOSITS  37 

sources  and  transported  to  a  single  place  hundreds  of  miles  away.  Espec- 
ially is  this  true  when  we  remember  that  coarse  and  fine  are  intimately 
comminorled/and  that  the  material  came  from  various  river  basins. 

LIST   or  ROCKS   FOUXD  IX   THE  TILL. 

A  list  of  several  kinds  of  rock,  represented  by  pebbles,  bowlders  and 
other  fragments  in  the  drift,  together  with  simple  means  of  identifying 
them,  is  given  below : 

Igneous   Rocks. 

(Rocks  solidified  by  cooling  from  a  hot,  molten  condition.) 

Granite.— Crystalline,  usually  coarse-grained,  speckled  appearance  due  to 
presence  of  many  separate  crystals  of  three  or  more  kinds  of  minerals,  chief 
among  which  are:  Quartz  (white  or  sugary,  and  very  hard);  Feldspar 
(whitish  or  reddish,  according  to  impurities  and  decayed  condition,  in  part 
with  somewhat  rectangular  outline,  and  "cleavage"  surfaces  which  reflect 
the  light,  hard);  Hornblende  (black,  or  greenish  black  if  decayed,  often  in 
small  irregular  bunches)  ;  Mica  (white  or  black,  cleaves  in  thin  flakes  which 
reflect  the  light  brilliantly,  soft  enough  to  be  cut  easily  with  the  knife).' 
Granite  is  sometimes  hard  to  distinguish  from  Gneiss. 

Diabase  or  Trap. — Crystalline,  coarse  to  fine,  dark  gray  or  black.  Among 
the  crystals,  black  minerals  such  as  Hornblende  predominate.  Feldspar, 
light  colored,  is  in  small  quantity.  Often  so  fine  grained  that  separate 
crystals  cannot  be  distinguished  without  lens. 

Quartz-Porphyry. — Dark  gray,  reddish,  or  pinkish  "ground  mass,"  in  which 
scattered  crystals  of  Quartz  or  Feldspar  may  be  distinguished  (Quartz,  color- 
less or  whitish:  Feldspar,  usually  straw  colored  or  flesh-colored,  latter  with 
rectangular  outline,  former,  usually  irregular). 

Amygdaloid. — Dark  colored,  often  black,  and  fine  grained,  with  "almond- 
shaped"  bunches  of  light  colored  substances  (usually  the  minerals  Quartz 
and  Calcite).  An  old  lava,  in  which  steam-bubble  cavities  have  been  filled  up 
by  deposits  from  percolating  waters. 

Sedimextaet  Rocks. 

(Originally  deposits  of  sediment,  or  organic  substances,  or  chemical  pre- 
cipitates, under  water,  hardened  by  pressure  of  overlying  sediments,  or  by 
heat,  or  by  some  natural  cementing  substance.) 

Limestone  or  Dolomite. — Gray  or  buff-colored,  varies  from  coarse  crystalline 
texture  to  very  compact  fine  grain.  Limestone  is  largely  lime  carbonate,  and 
unless  very  impure  will  effervesce  when  dilute  hydrochloric  acid  is  applied. 
In  Dolomite  there  is  some  carbonate  of  magnesium,  and  other  impurities, 
and  it  does  noj;  commonly  respond  readily  to  this  chemical  test.  It  is  not 
very  hard,  and  will  scratch  with  a  knife.  Formed  chiefly  by  the  deposition 
of  ground-up  shells  and  skeletons  of  marine  animals,  together  with  some 
mud  or  ooze,  frequently  rich  in  fossils. 

Chert. — Harder  than  steel,  flinty;  where  freshly  broken  it  has  a  sharp  frac- 
ture and  dull  greasy  luster,  dull  yellow,  gray,  or  brown,  common  in  lime- 
stone both  as  irregular  lumps  or  "nodules"  and  in  thin  beds.  In  part,  at 
least,  derived  from  siliceous  sponges  which  were  buried  by  sediments  on  the 
sea  floor. 

Sandstone. — Grains  of  sand  bound  together  into  a  gritty,  often  crumbly 
mass;  color  depends  largely  upon  the  cementing  substance;  red,  yellow,  or 
brown,  if  the  cement  is  iron  oxide;  white  if  it  is  silica;  grains  largely  Quartz; 
sometimes  flakes  of  Mica. 


^8  THE   DES  PLAINES  VALLEY.  [bull    no.  11 

.S'fta7t'. — Hardened  clay  or  nuid;'  greenish  gray,  dark  brown,  or  black;  soft, 
easily  scratched  with  a  knite;  yields  odor  of  clay  when  breathed  upon,  be- 
cause of  presence  of  kaolin. 

Quartz. — White,  except  as  stained  by  impurities;  too  hard  to  scratch  with 
steel;  glassy  where  broken.  Pebbles  are  fragments  of  Quartz  veins,  or 
fillings  of  fissures  in  other  rocks  by  deposits  of  silica  from  solution. 

Metamorpiiic  Rocks. 

(Originally  either  Igneous  or  Sedimentary  rocks,  greatly  altered  by  effects 
of  compression  or  deep  burial  in  the  earths'  crust,  or  in  some  cases  by  the 
extent  of  the  cementation.) 

Qunrtzite.—\eY\  hard,  fine  crystalline,  sugary  texture;  white,  pinkish, 
purplish,  or  dull  grayish;  formerly  a  sandstone;  re-crystallized  by  addition  of 
silica  deposited  from  solution. 

^7a/f.— Formed  from  Shale  by  compression.  Harder  than  Shale,  with  well 
defined  plane  of  splitting  or  cleavage. 

Marble.— 'LWiQ  Limestone,  but  distinctly  crystalline,  and  somewhat  harder. 
A  re-crystallized  Limestone. 

Gneiss.— A  banded,  crystallized  rock,  often  coarse  grained;  separate  crystals 
of  such  minerals  as  Quartz,  Feldspar,  Hornblende,  and  Mica,  arranged  in 
more  or  less  definite  bands,  and  thus  distinguished  from  Igneous  rocks 
Lighter  varieties,  with  much  Quartz  and  Feldspar,  resemble  Granite-  darker 
ones  often  largely  composed  of  pinkish  Feldspar  and  black  Hornblende  and 
Mica.  Most  Gneisses  seem  to  have  been  formed  from  Igneous  rocks  under 
great  pressure. 

In  the  following  table  is  the  number  of  pebbles  of  various  kinds  of  rock 
Identified  from  a  hundred  bits  of  rock  that  were  taken  indiscriminately  from 
a  cubic  foot  or  so  of  bowlder  clay  or  ice-laid  drift  at  two  different  places 
both  of  them  in  an  exposure  of  till  at  the  east  end   of  McEnty  street    in 
Joliet:*  ' 


First  Second 

collection,      collection. 


Limestone 
Sandstone. 

Shale 

Quartzite.. . 

Diabase 

Granite 


77        I  78 

8  10 

2  1 


Evidently  the  limestone,  most  of  which  has  presumably  come  from  close 
at  hand,  forms  about  three-quarters  of  the  stony  material.  The  sandstone  and 

nnr  h  »n°,  ^  ^.J^""!  ^l"""^  '^'^  Potsdam  and  Cincinnati  formations,  to  the 
north  and  northwest,  though  some  may  have  come  from  the  Devonian  rocks 
aulrt^;^^"''''  "^f"'  ^^^^^i^^n.  The  diabases  and  granites,  a^d  some  of  he 
250  or  300  miSs'  '"""'''""''  Wisconsin  or  beyond,  a  distTnce  of  at  least 

The  stratified  drift.— As  regards  the  variety  of  rocks  represented 
among  its  constitutent  bowlders,  pebbles  and  smaller  particles  the  ^trati- 
fJ""!!^  ^^^^"^^^^^  *^e  till.  The  material  that  composes  the'two  classes 
o±  drilt  were  picked  by  the  ice  from  a  common  collecting  around  and 
because  of  the  vast  extent  of  this  collecting  ground  thev  show  the  re- 
markable variety  indicated  in  the  last  few  pages.  The  features  peculiar 
to  stratified  drift  which  distinguish  it  from  till,  are  those  which  have 

_      ♦  Pebbles  identified  and  counted  by  Mr.  Charles  E.  Decker. 


GOLDTHVVAiT.]         GLACIAL    AND    INTER-GLACIAL    DEPOSITS  89 

been  effected  by  the  wearing  and  sorting  action  of  water.  While  the  ice 
sheet  meltetl:,  some  of  the  rock  waste  upon  and  within  it  found  its  way 
into  outflowing  streams,  wliich  washed  the  debris  along,  siiting  out  the 
finer  and  depositing  the  coarser  particles  in  such  places  and  at  such 
times  as  the  strength  of  the  currents  was  over-taxed.  Such  deposits, 
therefore,  are  in  layers,  because  of  the  repeated  changes  in  the  strength 
of  the  currents.  Coarse  gravel,  fine  gravel  and  sand  occur  in  successive 
beds,  in  the  order  of  their  deposition.  The  pebbles  have  been  more  or 
less  completely  rounded,  and  are  as  a  rule  arranged  flat  side  down, 
although  where  coarse  gravel  deposits  have  been  hurriedly  made  the 
constitutents  are  sometimes  poorly  arranged,  and  the  stratification  may 
be  obscure.  The  bedding  is  usually  nearly  horizontal-^-the  attitude  of 
a  stream  bed,  but  separate  layers  in  a  single  horizontal  stratum  may  be 
strongly  inclined — a  condition  known  as  "cross  bedding."  (See  Plate 
4,  A.)  This  peculiar  stratification,  in  many  instances,  marks  the  for- 
ward growth  of  a  sand  bar  or  a  delta.  The  slanting  layers  represent  suc- 
cessive positions  of  the  sloping  front  of  the  deposit,  as  it  Avas  advancing. 
After  a  large  mass  of  these  inclined  beds  has  been  laid  down,  the' cur- 
rents may  shift  in  direction  or  increase  in  strength,  in  such  a  way  that 
the  upper  part  of  the  deposit  may  be  cut  away  as  if  bevelled  and  a  new 
layer  may  be  formed  above  the  horizontal  surface  of  planation,  with  its 
beds  inclined  in  another  direction.  Where  currents  are  very  erratic  or 
tumultuous,  as  was  evidently  the  case  near  the  border  of  the  ice  sheet, 
the  cross  bedding  is  still  more  irregular.  No  horizontal  planes  of  bedding 
appear,  but  the  deposit  is  a  mass  of  lens-shaped  pockets  of  gravel  and 
sand,  dipping  in  various  directions — This  condition  is  Icnown  as  "flow 
and  plunge"  structure.  Examples  of  both  sorts  of  cross  bedding  can 
be  seen  in  Overholster's  gravel  pit,  near  the  south  end  of  Logan  avenue 
in  Joliet  (See  Plate  4,  A.) 

Stratified  drift  is,  for  the  most  part,  distributed  along  lines  of  initial 
dej)ression,  for  the  waters  discharging  from  the  ice  sheet  seek  the 
lowest  ground;  hence  it  happens  that  the  thickest  deposits  of  glacial 
gravels  in  this  district  (if  we  except  older  deposits  which  were  buried 
by  the  last  advance  of  the  ice)  are  to  be  found  along  the  Des  Plaines 
valley  and  the  valleys  of  the  larger  tributaries,  and  around  the  low  Chi- 
cago plain,  which  was  formerly  covered  by  a  great  lake.     " 

Large  deposits  of  stratified  drift  occur  about  Joliet.  On  the  south- 
east side  of  the  city  a  high  ridge  of  gravel  starts  in  at  the  bend  of  the 
Michigan  Central  railroad  near  Hickory  creek,  and  runs  south  and  south- 
west across  Powell  avenue.  On  its  southeast  side  the  gravel  deposit 
formerly  extended  off  with  gentle  slope  to  the  base  of  the  moraine;  but 
the  gravels  have  been  widely  excavated  for  railway  ballast.  Presh  cut's 
near  Powell  aveniie  show  exceedingly  coarse  gravel  with  occasional, 
bowlders.  This  greater  coarseness  of  gravel,  together  with  the  steep- 
ness of  slope  on  the  northwest  side  of  the  deposit,  in  contrast  to  the 
gentle  slope  towards  the  east,  suggests  that  the  gravels  were  washed  out 
from  a  tongue  of  ice  which  lingered  in  the  valley  while  the  main  border 
'of  the  ice  was  on  the  Valparaiso  moraine  to  the  east,  and  which  at  length 


40 


THE    DES  PLATNES    VALLEY. 


[BULL.   NO.   11 


melted  away,  allowing  the  gravels  iu  contact  with  it  to  slip  down,  form- 
ing a  steep  slope.  The  form  of  the  ridge  varies  greatly  as  it  runs 
south,  gaining  at  times  a  steep  slope  on  hoth  sides.  In  places,  however, 
the  steepness  of  the  slopes  seems  clearly  due  to  lateral  erosion  of  Hickory 
creek  on  the  one  side  or  of  the  old  outlet  on  the  oth'er;  for  the  Des 
Plaines  valley  for  a  time  was  occupied  by  a  large  river  which  discharged 
from  Lake  Chicago.  It  may  be  that  all  these  steep  slopes  are  to  be  ac- 
counted for  thus,  by  erosion,  rather  than  by  previous  contact  with  the 
ice  edge  and  the  removal  of  that  support. 

At  Overholser's  pit,  near  Linden  heights,  is  a  fresh  forty  foot -sec- 
tion of  cross-bedded  sands  and  gravels,  which  here  form  the  outer  border 
of  the  main  Valparaiso  moraine.  The  cross-bedded  layers  (as  seen 
in  Plate  4,  A)  show  a  rather  persistent  dip  towards  the  west,  indicating 


Fig.  S.  Diagram  showing  the  border  of  the  ice  resting  against  the  outer 
morainic  ridge  of  the  Valparaiso  system,  near  Joliet,  Lockport,  and  Romeo.  Four 
transverse  passages  are  occupied  by  glacier-fed  streams,  and  are  being  aggraded 
with  gravel.  The  passage  nearest  the  foreground  later  became  the  course  of  the 
Chicago  outlet,  and  finally  of  the  Des  Plaines  river.  The  one  next  to  the  left  is 
the  "big  slough"  north  of  Joliet. 

that  the  growtk  of  the  deposit  was  to' the  westward.  The  relations  to 
the  A^alparaiso  moraine  suggest  that  this  is  part  of  a  smooth  fan-like 
deposit  or  "frontal  apron,"  washed  forward  from  the  ice  while  it  lav 
against  tlic  inorainc.  The  plain  which  separates  the  main  ridge  from  tlu," 
wi'st  ridge  of  the  Valparaiso  morainic  system  south  of  Joliet  may  be  the 
surface  of  a  part  of  the  same  frontal  apron.  The  deposit  is  of  special 
interest  liecause  it  resembles  in  structure  a  much  older,  gravel  deposit, 
the  Joliet  conglomerate  described  later. 


STATE  GEOLOGICAL,  SURVEY. 


BULL.  NO.   11,  PL.  4. 


A.     Stratified   drift   at   Overliolser's   pit,    Joliet. 


^„i*.««>«i^^ 


B.     Exposure  of  Joliet  conglomerate   near  Spring  creek. 


UOLDTHWAIT.]         GLACIAL    AND    INTER-GLACIAL    DEPOSITS. 


41 


The  chief  deposits  of  gravel,  which  took  place  in  the  valleA's  whicli 
were  the  main  lines  of  drainage  while  the  ice  was  melting,  are  called 
"valley  trains.''  The  Des  Plaines  valley  from  Lemont  down  past  Joliet 
to  Channahon,  evidently  received  a  thick  deposit  of  this  outwash,  for  it 
was  the  main  line  of  escape  for  the  glacial  waters  with  their  over-burden 
of  rock  Avaste.  The  original  valley  floor  was  built  up  b}^  these  deposits 
locally  some  fifty  feet.  At  the  same  time,  tributary  streams  built  branch 
valley  trains.  Tliis  was  the  case  in  the  valleys  of  Long  run.  Fraction 
run,  Spring  creek  and  Hickory  creek  (See  Plate  5,  A.)  This  process  is 
ijlustrated  in  Figs.  8  and  9.  At  a  later  time,  when  the  ice  sheet  had 
withdrawn  from  the  Valparaiso  moraine,  the  over-loaded  ice-fed  stream 
in  the  Des  Plaines  valley  was  replaced  by  a  river  which  issued  from  a 


Fig.  9.  A  later  stage  than  that  of  Fig.  S.  The  ice  border  has  receded  to  the 
east  side  of  the  Valparaiso  moraine.  Aggrading  rivers  from  it  pass  down  the 
valleys  of  Hickory  creek,  Spring  creek,  Fraction  run.  Long  run,  the  "Sag,"  and  the 
Des  Plaines  valley.  Distributaries  occupy  the  transverse  passages  in  the  outer 
Tidge.  in   the  foreground. 

great  ice-front  lake,  and  which,  free  to  gather  up  a  load  for  itself,  exca- 
vated a  deep,  wide  trench  in  the  valley  filling,  carrying  away  most  of  the 
deposits.  Only  a  few  scraps  of  the  old  valley  train  were  left  as  terraces, 
e.  g:,  o^jposite  Lockport,  and  three  miles  west  of  Joliet,  or  as  flat-topped, 
island-like  mounds  in  mid-channel,  like  Flathead  mound  l^etween  Joliet 
and  Channahon.  These  are  mentioned  more  particularly  on  later  pages. 
,It  is  of  interest,  however,  to  note  here  that  in  certain  places  (e.  g.,  in  the 
outwash  terrace  opposite  Lockport)  the  pebbles  in  the  gravel  have  been 
coated  over  with  a  white  crust  of  carbonate  of  lime,  left  by  percolating 
water.  Sometimes  this  film  of  lime  carbonate  is  an  eighth  of  an  inch 
thick,  and  serves  to  bind  a  few  pebbles  together  (See  Xo.  3,  Plate  3)  : 
but  in  no  place  has  cementation  progressed  far. 


42  THE   DES  PLAINES   VALLEY.  [bull.  no.  U 

ff 

Along  each  side  of  the  Des  Plaines  valley  above  Lemont,  gravels  are 
to  be  found  where  artilicial  cuttings  have  been  made.  At  Kellar's  brick- 
yards, a  mile  north  of  Willow  Springs,  a  freshly  cut  bank  sixty  feet  high 
shows  stratilied  gravels  and  sands  beneath  ten  to  twenty  feet  of  till.  The 
gravels  there  may  belong  to  a  distinctly  older  interval  than  that  which 
followed  the  last  stage  of  glaciation. 

The  stratified  gravels  exposed  in  the  upper  part  of  the  Des  Plaines 
basin,  on  and  near  the  Chicago  plain,  are  chieflv  in  the  form  of  beach 
ridges,  spits,  and  other  shore  deposits  of  the  extinct  glacial.  Lake  Chi- 
cago. While  to  some  extent  they  may  be  regarded  as  stratified  drift^ 
they  were  formed  for  the  most  part  long  after  the  ice  had  withdrawn 
from  our  district,  and  its  influence  on  them  was  quite  indirect.  Lixe 
the  gravels  in  aprons  and  deltas,  they  often  show  cross  bedding. 

THE  JOLIET  CONGLOMERATE. 

At  several  places  in  the  vicinity  of  Joliet,  there  are  exposures  of  gravel 
firmly  cemented  by  carbonate  of  lime  into  a  conglomerate.  Judging 
from  its  composition  and  its  relations  to  the  overh'ing  Wisconsin  till, 
this  coBglomerate  represents  one  of  the  earlier  interglacial  epochs.  The 
largest  and  most  instructive  exposure  so  far  observed  is  at  the  east  end 
of  JMcEnty  avenue,  near  the  old  wire  mill,  and  on  the  north  side  of 
Spring  creek  (Plate  4,  B.)  The  cemented  gravels  here  are  immediately 
overlain  Ijy  late  Wisconsin  till.  Another  outcrop,  better  known,  but  of 
less  significance,  since  it  is  buried  by  outwash  gravels  ratlier  than  till, 
and  thus  looks  at  first  sight  like  a  locally  cemented  mass  of  the  late 
Wisconsin  gravel  deposits,  occurs  at  the  bend  of  the  Michigan  Central 
railway,  a  short  distance  west  of  the  pumping  station  in.  Joliet.  Tlie  rock 
also  outcrops  nearby  on  Cass  street.  A  large  amount  of  the  conglojnerate 
was  excavated  at  this  place  a  number  of  years  ago.  The  ledge  that  re- 
mains, close  beside  the  tracks,  is  some  ten  feet  high.  In  the  bed  of  Bush 
creek,  in  Eeed's  woods,  the  surface  of  the  conglomerate  is  seen  where  the 
stream  is  trimming  back  a  spur  at  the  side  of  its  ravine.  On  the  map, 
Plate  7,  "Cg."  indicates  this  outcrop  of  the  conolomerate.  It  looks  as 
if  the  rock  belonged  under  the  till  of  which  the  Ijank  is  composed. 
The  conglomerate  liere  is  of  finer  texture  than  usual,  but  in  other  re- 
spects seems  to  be  like  that  at  other  exposures.  As  only  a  thin  layer 
is  exposed  here,  one  cannot  judge  either  of  the  extent  or  of  the  average 
structure  of  the  entire  mass  that  may  underlie  the  bowlder  clay  in  the 
bank.  This  exposure  is  about  three  and  a  half  miles  southeast  of  the 
one  near  Spring  creek.  In  a  railway  cut  on  the  Elgin,  Joliet  and  Eastern 
railway,  near  Eowell  avenue,  in  the  extreme  southeast  part  of  Joliet, 
ten  feet  of  till  covers  a  coarse  gravel  deposit  which  is  in  places  well 
cemented  with  carbonate  of  lime  and  limonite  (hydrous  oxide  of  iron). 
Nowhere  else  has  -a  limonite  cement  been  noted.  This  rock  is  doubtless 
the  same  formation  as  those  mentioned  elsewhere. 

Another  outcrop  appears  in  the  bluff  on  the  east  side  of  the  outlet  valley 
just  north  of  Lockport,  close  beside  the  Chicago  and  Joliet  trollev  line. 


S'TATE   GEOLOGICAL.   SURVEY. 


BULL.    NO.    11,    PL.    5. 


A.     Outwash    terrace    on    Spring    creek. 


B.     Fraction  run  above  Dellwood  Parle. 


r  m.m  v*^ 


«.  ^  m  ■' 


A     «     .  ^VAV.^A 


J 


GOLDTHWAIT]         GLACIAL    AND    INTER-GLACIAL    DEPOSITS.  43 

This  shows  eight  feet  of  tlie  rock,  with  the  lower  limit  not  exposed.  This 
exposure  is  about  seven  miles  north-northeast  of  the  Bush  creek  outcrop, 
and  four  miles  north  of  the  one  at  Spring  creek.  Talus,  which  appears 
in  the  bluff  still  farther  north,  near  Eomeo,  looks  suspiciously  like  the 
cemented  conglomerate.  Eeports  of  a  "hardpan"  underlying  the  till 
along  the  line  of  the  Chicago  drainage  canal,  a  mile  or  so  east  of  Sum- 
mit^ suggest  that  the  conglomerate  covers  even  a  wider  area  than  that 
marked  by  the  outcrops  just  mentioned.  Doubtless  as  further  search 
is  made  the  known  extent  of  the  formation  will  be  greatly  increased,  as 
well  as  the  understanding  of  its  origin.  The  following  data  concerning 
the  Spring  creek  exposure  was  collected  by  Mr.  C.  E.  Decker. 

The  conglomerate  outcrops  in  a  large  artificial  exposure  beneath  the 
till  of  the  Valparaiso  moraine  (See  Plate  4,  B.)  From  the  base  of  the 
till  to  the  bottom  of  the  excavation  the  exposure  of  cemented  gravels  is 
about  eighteen  feet.  The  overlying  till  is  very  compact,  and  chiefly 
composed  of  fine  rock  flour,  with  a  moderate  supply  of  small  stones, 
some  of  which  are  striated  and  most  of  which  are  subangular.  The 
stones  of  the  till,  classified  according  to  'composition  and  given  in  per- 
centages, has  already  been  given.  The  till  is  separated  from  the  under- 
lying conglomerate  by  a  well  defined  plane  of  unconformity.  The  till 
immediately  above  the  unconformity  shows  no  signs  of  cementation. 
The  surface  of  the  conglomerate  is  smooth,  though  locally  marked  by 
semi-parallel  ridges  an  inch  or  two  across  and  rather  faint  in  expression, 
yet  distinct  enough  to  convey  the  impression  that  they  may  be  marks  of 
the  late  Wisconsin  ice  sheet.  They  trend  northeast-southwest.  The 
surface  does  not  appear  to  have  been  striated,  however,  nor  do  there  ap- 
pear to  be  any  ridges  of  the  shaly  matrix  of  the  conglomerate  in  the  lee 
of  projecting  pebbles,  where  such  ridges  might  be  expected  to  develop. 
At  the  top  of  the  cemented  section  is  a  dense  shaly  layer  of  rock,  buff 
colored  and  thinly  laminated  in  a  horizontal  plane.  It  seems  never  to  be 
more  than  an  inch  or  two  thick.  Beneath  it  come  about  six  feet  of  hori- 
zontally bedded  gravels,  fine  at  the  very  top  and  moderately  coarse  be- 
low. The  uppermost  three  inches  are  well  cemented ;  below  that  is  a  zone 
of  about  a  foot  and  a  half  of  loosely  bound  gravels,  and  then  again  the 
firmly  cemented  material.  Most  of  the  pebbles  in  these  horizontal 
beds  are  well  rounded,  although  many  are  sub-angular.  Below  this  six 
foot  stratum  come  four  feet  of  cross-bedded  gravels  of  much  coarser 
texture;  more  than  one-half  the  pebbles  in  this  are  sub-angular  to  an- 
gular, and  all  are  arranged  flat  side  down  on  the  inclined  beds,  Avhich 
dip  25  degrees  toward  the  southwest.  They  may  be  seen  in  the  photo- 
graph, PI.  4,  B.  Beneath  this  is  a  confused  mass  of  angular  blocks, 
cobbles  and  coarse  gravel,  containing  bowlders  two  feet  in  diameter. 
The  interstices  are  not  all  filled,  leaving  the  gravel  with  an  open-work 
structure.  No  bedding  could  be  discovered.  A  large  majority  of  the 
fragments  of  rock  are  angular,  but  none  were  found  with  striated  sur- 


1  Geological   Atlas   of  the  Unitea   States,   U.    S.    Geol.    Surv.,    Chicago   Folio   No. 

SI,    p.    7. 


44 


THE    DES  PLAINES    VALLEY, 


[BULL.    NO.   11 


faces.  It  slioukl  be  said,  also,  that  tlie  cjcgree  of  cementation  varies 
locally  in  a  horizontal  direction  as  well  as  in  a  vertical.  This  gives  ri^e 
to  irregular  projections  and  re-entrants  in  the  cliff  exposure. 

A  careful  study  was  made  of  the  pebbles  in  the  conglomerate  in  ord'-r 
to  determine  the  variety  of  rocks  represented  and  the  proportion  of  each. 
Without  any  choice  as  to  size,  one  hundred  pebbles  were  selected  at 
.  random  from  a  small  space  on  the  face  of  the  cliff,  and  the  pebbles  were 
identified  and  counted.  This  was  done  at  three  places,  with  the  results 
which  follow.  Since  each  set  includes  100  pebbles,  the  figures  for  each 
kind  of  rock  represent  percentages. 


Position.                          Limestone      Chert. 

Sandstone.    Granite. 

Diabase. 

Half  way  up  c! iff 

83 
88 

I 
2 

3 
3 
5 

4 
2 

4 

3 

At  same  level,  wiiliiii  10  feet  of  No.  1 
Near  top  of  cliff,  and  50  feet  away... 

2 

1 

The  table  shows  a  pretty  close  agreement  in  the  three  counts,  in  making 
the  limestone  content  al^out  86  per  cent  of  the  whole.  The  limestone  and 
the  chert  are  probably  almost  wholly  derived  from  the  Niagara  limestone, 
the  bed  rock.  Apparently,  then,  about  80  or  90  per  cent  of  the  gravels 
are  of  local  derivation.  The  percentage  of  crystallines  (chiefly  granites 
and  diabases,  although  some  are  probabl}^  to  be  regarded  rather  as 
gneisses)  is  very  small,  less  than  five  per  cent.  But  their  igeneous  char- 
acter indicates  a  remote  .source  for  at  least  a  part  of  the  deriosit.  The 
crystallines  probably  do  not  exist  in  place  nearer  than  the  highlands  of 
northern  Wisconsin,  some  300  miles  away.  All  the  large  cobbles,  bowld- 
ers and  angular  blocks  seemed  to  be  of  limestone.  The  granites  and  dia- 
bases were  well  rounded  pebbles  of  medium  and  small  size,  as  would  be 
expected  from  their  having  journeyed  many  times  as  far  as  the  others. 

The  outcrop  of  the  Joliet  conglomerate  at  Lockport  shows  about  the 
same  projiortions  of  different'  sorts  of  rock,  with  perhaps  a  slightly  larger 
number  of  granite  and  diabase  pebbles,  say  5  to  10  per  cent.  No  coarse, 
angular  material  is  exposed  there  at  the  base.  The  rock  is  cemented  just 
as  firmly  as  at  Spring  creek. 

It  may  be  said  tli-at  the  percentage  of  local  fragments  (limestone  and 
chert)  in  the  cemented  gravels  is  about  the  same  as  in  the  late  Wisconsin 
till  at  the  same  locality  for  the  latter. shows  about  78  per  cent,  as  against 
the  86  per  cent  in  the  older  material.  The  till  was  found  to  contain  about 
12  per  cent  of  crystalline  ])ebbles — a  somewhat  larger  number  than  were 
found  in  the  conglomerate  at  Spring  creek. 

On  the  basis  of  these  facts,  some  conjectures  may  be  formed  concern- 
ing the  origin  of  the  Joliet  conglomerate.  That  it  is  a  glacial  gravel  de- 
posit seems  clear  from  the  variety  of  rocks  represented  in  the  pebbles. 
No  such  collection  Avould  be  at  all  likely  to  be  made  by  any  conceivable 
river  or  lake  in  this  district.  That  it  is  older  than  the  late  Wisconsin 
drift  as  indicated  by  tlic  fact  that  it  is  unconformably  covered  In'  the  till 
of  the  Valparaiso  moraine.  It  is  of  some  significance  also  that  the  bed- 
ding of  the  conglomerate,  close  to  the  surface,  shows  no  sign  of  folding  or 


GOLDTHWAiT.]         GLACIAL   AND    INTER-GLACIAL   DEPOSITS.  45 

other  disturbance.  One  would  be  inclined  to  infer  that  the  gravels  were 
already  cemented  when  they  were  over-ridden  by  the  ice,  else  their  strati- 
fication would  have  been  disturbed  by  pressure.  The  glaciated  appear- 
ance of  the  surface  of  the  conglomerate  and  the  imaltered  condition  of 
the  overlying  till  argues  likewise  for  pre-Wisconsin  cementation.  Judg- 
ing from  the  advanced  state  of  cementation  in  which  a  well-nigh  solid 
rock  has  been  formed  out  of  gravels,  a  time  interval  of  very  considerable 
length  must  have  ^lapsed  after  the  gravels  were  deposited  and  before 
the  late  Wisconsin  glaciation.  If  the  conglomerate  is  compared  with  the 
nwve  recent  outwash  gravels,  even  those  for  instance  in  the  outwash 
terrace  opposite  Lockport  which  show  more  than  the  usual  amount  of 
cementation,  the  alteration  of  the  former  obviously  represents  several 
times  the  amount  of  alteration  of  the  latter,  and  we  may  infer  that  it 
is  several  times  as  old.  Turning  now  to  the  conjectured  time  relation 
for  the  several  glacial  epochs,^  we  find  that  tlie  interval  since  the  early 
Wisconsin  is  estimated  to  be  about  twice  the  post-glacial  interval,  the 
one  since  the  lowan  four  times,  since  the  Illinoian  eight  times,  since 
the  Kansan  sixteen  times,  and  since  the  Jerseyan  a  very  much  longer 
time.  It  seems  probable,  theu,  from  the  extent  of  cementation  (and  all 
that,  perhaps,  before  the  overlying  till  was  deposited)  that  the  Joliet 
conglomerate  is  at  least  as  old  as  the  Illinoian  drift. 


1  See  Chamberlin  and  Salisbury,  "Geology."  vol.  3,  pp.  413-414. 


46  THE   DES  PLAINES   VALLEY.  [bull.  no.  11 


CHAPTER  V. 


PHYSIOGEAPHIC  HISTORY  OF  THE  LOWER  DES  PLAINES 

RIVER. 

GENERAL  DESCRIPTION, 

The  lower  Des  Plaines  river  follows  a  flat-floored,  steep-sided  valley, 
wliich  was  cut  down  across  the  broad  A'^alparaiso  morainic  system  by 
the  large  river  that  drained  the  Great  Lakes  during  the  closing  stages 
of  the  glacial  period.  This  valley,  inlierited  by  the  Des  Plaines  from 
the  ancestral  river,  the  outlet  of  Lake  Chicago,  far  exceeds  the  dimen- 
sions appropriate  to  the  streams  present  size  and  sculpturing  ability. 
With  a  somewhat  devious  course,  the  channel  of  the  old  outlet  leads  from 
the  lake  plain  near  Summit  (See  Fig  10)  westward  and  southeastward 
through  the  broad  upland  belt  of  the  Valparaiso  moraine,  uniting  just 
beyond  its  outer  border  with  the  Kankakee  river,  on  the  broad,  low 
plain  of  the  "Morris  basin."  Between  Summit  and  Lemont  the  river 
flows  by  a  directly  transverse  course  through  the  main  moraine,  and 
gathers  scarcely  any  drainage  except  the  direct  run-off  from  the  high 
bluffs  on  either  side  of  the  valley.  But  beyond  Lemont  its  course  is 
southward  along  the  outer  border  of  the  main  moraine,  from  which  it 
receives,  a  large  number  of  tributary  creeks.  Of  these.  Long  run.  Spring 
creek  and  Hickory  creek  drain  considerable  areas  in  the  interior  of  the 
moraine,  and  widen  the  drainage  basin  of  the  Des  Plaines  over  ten  miles 
on  the  east  side.  Beyond  Joliet  the  outlet  valley  opens  on  the  broad 
-plain  which  surrounds  the  junction  of  the  Des  Plaines,  Du  Page  and 
Kankakee  rivers.  The  Du  Page  joins  the  Des  Plaines  so  close  to  its 
mouth  that  physiographically  it  might  as  well  be  considered  a  direct 
tributary  of  the  Illinois.  Its  basin  is  enclosed  by  the  Minooka  till  ridge, 
on  the  west,  and  an  outlyiug  ridge  of  the  Valparaiso  morainic  system 
on  the  oast.  • 

In  arldition  to  these  larger  features,  certain  details  of  geologic  struc- 
ture and  physiographic  form  along  the  lower  Des  Plaines  demand  ex- 
planation— Among  these  may  be  mentioned  :  The  relation  of  the  extinct 
outlet  to  the  bed  rock,  which  rises  to  a  considerable  height  in  the  bluffs 
at  two  places  (Lomont  and  Lockport)  :  the  high  level  terraces  of  gravel, 
conspicuous  at  several  points  below  Romeo,  and  terminating  near  the 
liearl  of  the  Illinois  at  Channahon ;  a  lower  terrace  of  rock  on  both  sides 
of  the  valley  near  Lockport,  and  the  terraces  of  tributary  streams. 


GOLDTHWAIT. 


HISTORY   OF    THE    LOWER    DES  PLAINES. 


47 


In  order  to  understand  the  physical  features  of  the  valley,  we  shall 
follow  the  development  of  successive  moraines  and  outwash  deposits 
along  the  retreating  ice-border,  the  formation  and  the  gradual  extinc- 
tion of  ice-dammed  lakes,  and  the  steps  in  the  cnttiug  down  of  the 
great  Chicago  outlet. 

DEPOSITIOX    OF    THE    EARLY    WISCONSIN    DRIFT. 

The  early  Wisconsin  moraines. — The  outline  of  the  border  of  the 
Wisconsin   ice-sheet   in   Illinois   at   the   time   of   its   greatest   extent   is 


•'  Valparaiso 

Morg/ne. 

'i\(kMinooha  T//J 
Ridge. 


2  — r= 

M/UES. 


Fig.  10.  Map  of  the  lower  Das  Plaines  river,  showing  towns,  tributaries,  and 
distribution  of  drift.  Rv,  Riverside  ;  S,  Summit ;  Wi,  Willow  Springs ;  Lm,  Lemont ; 
Ro,  Romeo ;  Lk,  Locliport ;  J,  Joliet ;  N.  L,  New  Lenox  ;  C.  Cliannahon  ;  Wh, 
Wheaton ;  Na,  Naperville ;  Au,  Aurora ;  1,  Salt  creek ;  2,  Chicago  river ;  3,  Flag 
creek  ;  4,  Calumet  river  ;  5.  Long  run  ;  7,  Fraction  run  ;  8,  Spring  creek  ;  9,  Hickory 
creek;  10,  Sugar  creeli ;  11,  Jackson  creek;  12,  Prairie  creek;  13,  Rock  creek;  14, 
Dupage  river;  15,  Ausable  creek:  16,  Fox  river;  17.  Buffalo  creek;  18,  Isle  la 
Cache  creek;  19,  Mink  creek;  20,  Crystal  run.  Drift  plotted  from  U.  S.  Geol.  Surv., 
Monog.  38,  by  Leverett,  with  minor  changes. 

shown  on  the  sketch  ma]D  (Figure  G).  Its  ]30sition  is  marked  out  by  the 
broad  Shelb3'-ville  moraine,  a  continuous  belt  of  drift  built  up  along 
the  ice  margin,,  when,  for  a  considerable  time,  the  backward  melting  of 
the  ice  was  more  or  less  evenlv  balanced  bv  forward  motion,  and  the 


48  THE    DES  PLAINES    VALLEY  [bull.  no.  U 

ice  border  remained  almost  stationary.  When,  tli rough  the  intiueuce  of 
climatic  change,  the  melting  of  the  ice-front  came  to  exceed  its  advance, 
the  ice  border  was  sliifted  northeastwtird.  The  Illinois  lobe  of  the  ice 
sheet  contracted  to  lit  the  Lake  Micliigau  basin.  The  withdrawal  was 
slow  and  frequently  interrupted  by  short  returns  of  severer  climate, 
during  which  the  ice  border  became  stationarv,  or  even  re-advanced 
slightly.  Each  time  it  halted  it  built  a  new  morainic  ridge,  whose  size 
is  roughly  proportional  to  the  duration  of  the  period  of  re-advance. 
Between  the  moraines  the  drift  was  spread  out  in  gently  undulating 
plains  of  till. 

One  of  the  most  conspicuous  of  these  crescentic  moraines,  the  Mar- 
seilles moraine,  lying  just  east  of  the  Fox  and  Vermilion  rivers,  forms 
the  semi-circular  rim  of  the  Morris  basin — a  l)road,  flat  plain  on  whose 
eastern  border  the  Des  Plaines  and  Kankakee  rivers  unite  to  form  the 
Illinois. 

The  lake  in  the  Morris  basin. — The  retreat  of  the  ice  border  from 
/his  moraine  seems  to  have  left  a  lake  of  considerable  size  in  the  ^lorris 
basin,  which  found  its  discharge  over  the  lowest  point  on  the  morainic 
rim,  near  Marseilles.  Beaches  built  along  its  shores  indicate  that  its 
level  was  fullv  sixtv  feet  above  the  river,  or  050  feet  above  the  sea. 
As  the  outflow  cut  its  channel  down  through  the  moraine,  it  encomitere<l 
the  underlying  bed  rock  at  an  altitude  of  about  560  feet.  This  probably 
explains  the  fact  that  the  lake  level  remained  stationary  long  enough 
for  distinct  beaches  to  be  formed.  Indeed,  as  will  j^resently  be  explained, 
there  is  good  reason  to  suppose  that  the  lake  was  still  in  existence  at 
the  5G0-foot  level  when  the  ice  was  making  the  A'alparaiso  moraine, 
ten  or  fifteen  miles  farther  east. 

DEPOSITIOX  OF  THE  LATE  WISCONSIN  DRIFT. 

TJtP  Minoola  till  ridge. — Following  the  development  of  the  lake  in 
the  Morris  basin,  and  before  the  construction  of  tlie  next  system  of  mor- 
aines occurred  a  shifting  of  the  ice  lobes  in  northwestern  Indiana,  as 
a  result  of  which  the  late  Wisconsin  moraines  overlap  the  earlier  mor- 
aines in  transverse  position  (See  Figure  6).  There  was  evidently  a 
sudden  growth  of  the  Erie  and  Saginaw  lobes  of  the  continental  glacier, 
a  growth  which  pushed  them  westward  over  the  territory  which  had 
formerly  been  occupied  by  the  Lake  Michigan  lobe.  The  discordant 
relation  of  the  two  'sets  of  moraines  and  the  somewhat  subdued  topo- 
graphy of  the  earlier  set  have  led  to  the  separation  of  the  Wisconsin 
epoch  into  an  early  and  a  late  Wisconsin  stage.  In  the  district  we  have 
to  consider,  the  Marseilles  moraine  is  the  last  of  the  early  Wisconsin 
moraines,  and  the  !Minooka  till  ridge ;  a  small  morainic  ridge  forming 
the  east  side  of  the  Morris  basin,  is  the  first  of  the  late  Wisconsin  mor- 
aines. 

The  !Minooka  till  ridge,  from  the  head  of  the  Illinois  river,  where  it 
is  from  100  to  110  feet  high,  northward  for  fifteen  to  twenty  miles,  is 
"a  single  smooth  ridge  on  whose  crest  and  slopes  there  are  few  swells 
exceeding  ten  feet  in  height."     It  is  scarcely  two  miles  wide.     ''The 


GOLDTHWAiT.J  HISTORY    OF    THE    LOWER    DES  PLAINES.  49 

ridge  is  crossed  by  two  valley-like  depressions,  Avhicli  unite  near  its 
western  edge,  in  Sec.  13,  T.  36,  E.  8  E.,  and  drain  west  into  Au  Sable 
creek.  These  are  cnt  down  to  the  level  of  the  plain  on  the  east  side 
of  the  ridge.  They  apparently  were  formed  by  the  discharge  of  water 
from  the  ice  margin  or  ponded  between  the  ridge  and  the  receding  ice 
front.'^i 

South  of  the  river  only  a  few  low,  broken  mounds  and  ridges  of 
drift  mark  the  continuation  of  the  ice  border  at  this  stage. 

The  Valparaiso  morainic  system  and  its  outioasJi. — The  next  station- 
ary position  of  the  ice  border  was  one  of  long  duration,  resulting  in  the 
building  of  the  highest  and  broadest  of  the  morainic  belts  with  which 
we  are  here  concerned — the  Valparaiso  morainic  system.  This  is  a 
great  U-shaped  belt  of  drift  that  encircles  the  south  end  of  Lake  Mich- 
igan, with  its  course  about  twenty  miles  back  from  the  lake.  It  is  not 
a  single  ridge  like  the  moraines  just  described,  but  a  belt  in  which, 
in  our  district  three  parallel  belts  of  morainic  hills,  separated  by 
two  narrow  plains  of  drift  may  be  distinguished.  The  other  ridge 
separates  the  Du  Page  and  Des  Plaines  valleys  north  of-Joliet.  It  is 
itself  separated  from  the  middle  morainic  belt  southeast  of  Joliet  by  a 
fainting  undulating  plain,  which  narrows  as  it  approaches  the  State  line, 
allowing  the  outer  and  middle  belts  to  merge  into  one. 

The  outer  ridge,  north  of  Joliet,  is  cut  transversely  by  three  well  de- 
fined channels,  or  scour-ways  (as  shown  in  Figure  10).  One  of  these, 
crossed  by  the  Plainfield  road  three  m  iles  northwest  of  Joliet,  is  a  broad, 
flat-floored  sag  nearly  half  a  mile  wide  and  four  miles  long.  It  is 
occupied  by  a  marsh,  which  drains  eastward  through  Crystal  run  and 
westward  through  Eock  run.  Moderate  slopes  on  either  side  lead  to  the 
morainic  upland.  The  floor  is  immediately  underlain  by  bed  rock, 
which  is  shown  in  small  quarry  diggings  a  mile  east  of  the  Plainfield 
road.  At  its  eastern  end,  the  floor  of  the  sag  finds  continuation  in  a 
rock  terrace  of  the  Des  Plaines  valley  above  Joliet,  near  the  Sprague 
school  house.  A  few  feet  above  the-  marshy  floor,  oil  either  side,  is  a 
faintly  defined  sheet  of  gravel,  which  passes  into  a  distinct  terrace  at 
the  Des  Plaines  valley  to  the  eastward.  From  these  gravels  and  similar 
deposits  in  the  Des  Plaines  valley  at  several  points  below  Eomeo  it  ap- 
pears that  the  three  sloughs  north  of  Joliet,  and  the  Des  Plaines  valley 
just  below  Joliet,  were  lines  of  discharge  of  glacial  drainage  while  the 
ice  rested  against  the  outer  belt  of  the  Valparaiso  moraine.  Figure  3 
illustrates  this  condition  of  things.  As  the  ice  withdrew  to  the  position 
of  the  middle  belt,  the  inter-morainic  depression  between  Joliet  and 
Eomeo  gathered  the  discharge  of  heavily  loaded  streams  from  th? 
outer  slope  of  the  new  moraine  (See  Fig.  9).  Long  continued  aggrad- 
ing with  coarse  gravels  raised  the  level  of  the  inter-morainic  valley  up 
to  and  above  that  of  the  transverse  sloughs.  Water  from  the  ice  then 
flowed  through  them  and  deposited  trains  of  gravel  or  "outwasli."  At 
a   still  later  time,   after    the   ice  had   withdrawn   from   the   Valparaiso 


Leverett.  Monograph   38,   U.   S.   Geol.    Surv.,   p.   319. 

-4  G 


50  THE   DES  PLAIN ES   VALLEY.  [bull.  .no.  11 

« 

moraine  and  the  outlet  of  a  newly  formed  Lake  Chicago  found  its 
way  down  the  line  of  outwash,  aggradation  gave  way  to  degradation. 
The  floors  of  the  transverse  sloughs  were  reduced  by  the  overflow  from 
tlie  main  valley.  The  three  sloughs  north  of  Joliet  were  only  slightly 
lowered  before  the  streams  encountered  bed  rock.  The  one  in  which  tha 
rock  lay  deepest  below  the  surface  (that  south  of  Joliet)  was  degraded  so 
iiiuoh  the  more  rapidly  that  it  became  the  sole  line  of  discharge  of  the 
outlet  river,  while  the  three  rock-floored  passageways  north  of  Joliet 
became  sloughs.  During  the  lapse  of  several  thousand  years  marsli 
growth  has  built  up  the  floors  of  these  sloughs  and  running  water  has 
somewhat  smoothed  down  their  side  slopes. 

The  surface  of  the  main  belt  of  the  Valparaiso  moraine  is  more  typi- 
cally morainic  than  the  one  which  passes  west  of  Joliet,  although  its 
irregularity  is  nowhere  so  pronounced  as  to  exhibit  steep  slopes  compar- 
able to  the  "kettle  moraine"  of  Wisconsin  or  the  terminal  moraines  of 
many  other  places.  It  is  composed  of  numberless  knolls  and  basins. 
So  subdued  are  they  that  the  eye  hardly  appreciates  the  range  of  un- 
dulation, which  often  amounts  to  25  feet.  Over  the  greater  part  of  the 
moraine  the  knolls  show  a  tendency  to  elongation  parallel  to  the  mor- 
ainic belts,  but  on  the  inner  border  they  seem  rather  to  be  elongated  in 
the  direction  of  ice  motion.  On  account  of  the  compactness  of  the 
bowlder  clay  of  which  the  moraine  is  largely  composed,  little  ponds  and 
marshes  are  of  frequent  occurrence  in  the  depressions  of  the  moraine,  and 
peat  bogs  of  considerable  thickness  have  formed  in  the  deeper  de- 
pressions. The  cause  of  the  rolling  surface  of  the  moraines  has  been 
explained  on  previous  pages. 

Between  the  middle  and  the  east  belt  of  the  Valparaiso  morainic 
system,  is  a  rather  well  defined  plain.  Several  large  streams  which 
join  the  Des  Plaines  between  Eomeo  and  Joliet  head  here  in  broad 
marshes:  Long  run  and  Spring  creek  in  the  township  of  Orland,  and 
ITickory  creek  near  Tinley  park.  The  lower  courses  of  these  tributary 
valleys,  from  the  points  where  they  cross  the  middle  of  the  morainic 
belt  down  to  their  junctions  with  the  Des  Plaines,  were  lines  of  aggra- 
dation for  glacial  streams  during  the  whole  time  the  middle  moraine  ' 
was  being  deposited  (See  Fig.  9).  Together  with  the  inter-morainic 
depression  into  which  they  ran,  they  wore  heavily  aggraded  with  coarse 
ontwash  gTavels.  Patclios  of  the  old  valley  train  of  Hickory  creek  occur 
all  the  way  from  ISTew  Lenox  down  to  Joliet,  and  patches  of  the  valley 
train  of  Spring  creek  occur  below  Hadlov.  Where  the  valley  train-  head 
on  the  moraine,  they  partake  of  the  rolling  surface  which  characterize? 
the  ice-laid  drift,  for  these  gravel  deposits  at  the  immediate  l^order  of 
tlie  ice  were  subject  to  just  the  same  causes  of  irregular  concentration 
and  re-arrangement  as  the  moraine  itself.  But  down  the  valleys  their 
surfaces  become  as  smooth  as  the  flood  plains  of  the  present  streams. 
Fjast  of  Joliet  a  remnant  of  the  valley  train  of  Hickory  creek  forms  a 
conspicuous  terrace  near  the  old  red  mill.  Its  gravelly  constitution  may 
be  seen  below  the  iron  bridge,  where  the  river  is  freshly  trimming  the 
terrace,  or  at  the  gravel  pits  beside  the  Pock  Island  railwav.  just  west 
of  ShawV  lirick  yards.     On  Spring  creek,  above  the  old  wire  mill,  fine 


GOLDTHWAiT.I  HISTOKY    OF    THE    LOWER    DES  PLAINEST  51 

terraces  of  the  valley  ,train  stand  35  feet  above  the  present  flood  plain 
(Piste  5,  A.)  On  the  north  side  of  the  valley  fresh  cuttings  show  well 
stratified  gravely  frequently  cross-bedded,  the  constituents  varying  in 
size  from  cobblestones  to  fine  sand.  A  natural  section  occurs  a  few  hun- 
dred yards  east  of  the  wire  mill,  where  the  creek  is  trimming  away  the 
bluif.  At  the  base  of  this  section  the  compact,  blue  bowlder  clay  may 
be  seen  beneath  the  gravels. 

The  upper  portion  of  the  broad  valley  now  followed  by  the  Des  Plaines 
between  Mount  Forest  and  Eomeo,  as  well  as  the  "ISag,"  which  joins 
it  aboA-e  Lemont,  were  doubtless  transverse  depressions,  like  the  valleys 
of  Hickory  creek  and  Spring  creek,  and  were  deeply  aggraded  with  out- 
wash  gravels.  They  were  the  head  of  a  system  of  valley  trains,  as  in- 
dicated in  Fig.  10.  A  main  line  of  discharge,  to  which  they  were  tribu- 
tary, was  the  longitudinal  depression  between  the  middle  and  west 
morainic  belts.  The  floor  of  this  depression  was  evidently  built  up 
so  high  with  gravels  that  the  aggrading  stream  overflowed  all  four  passes 
through  the  west  ridge.  At  the  upper  end  of  the  pass,  near  the  Sprague 
school,  a  mile  north  of  the  end  of  the  Hickory  street  ear  line,  the  out- 
Avash  gravels  form  a  flat  terrace  on  the  west  side  of  the  main  valley. 
'J'his  is  but  a  small  scrap  of  the  flat-topped  valley  train  which  once 
filled  the  entire  valley.  The  heavy  cobbly  constitution  is  revealed  in 
a  pit  north  of  Frank  Sprague's  house,  where  the  road  to  Coyne's  station 
rises  from  a  rocky  bench  up  to  the  outwash  terrace.  Another  flat-topped 
remnant  of  the  valley  filling  is  on  the  west  side  of  the  valley,  opposite 
Lockport,  where  the  road  to  Plain  field  leaves  the  valley  floor.  The  flat 
surface  of  the  terrace  stretches  westward  several  hundred  yards,  to  the 
gently  imdulating  slope  of  tlie  moraine.  A  cut  by  the  roadside  shows 
the  gravels  to  be  locally  coated  and  cemented  with  carbonate  of  lime. 
The  incrustation  on  the  pebbles  attains  a  thickness  of  over  a  tenth  of 
an  inch   (See  Plate  3,  No.  3). 

The  height  (above  sea  level)  of  the  outwash  terrace  at  Lockport  is 
620  feet;  near  the  Sprague  school,  603  feet.  The  valley  filling  ex- 
tended south  and  west  past  Joliet  to  Channahon,  where  it  took  the  form 
of  delta-like  flats  at  the  border  of  the  lake  which  still  occupied  the 
Morris  basin.  Most  of  the  filling  was  removed  when  Lake  Chicago  came 
into  existence,  and  its  great  out-flow  following  the  main  line  of  glacial 
drainage,  excavated  for  itself  the  present  deep  valley.  Only  occasional 
scraps  were  left,  usuall}^  as  terraces  on  the  valley  sides,  like  those  de- 
scribed above. 

On  the  north  side  of  the  Des  Plaines  valley,  a  few  miles  below  Joliet, 
-the  outwash  terrace  is  broad  and  conspicuous.  The  upper  road  to  Chan- 
nahon follows  it  for  a  few  miles.  Out  in  the  middle  of  the  valley  is  a 
great  island-like  mound  known  as  '^"Flathead,"  which  marks  the  former 
extension  of  the  outwash  terrace  over  the  whole  valley.  This,  the 
largest  remnant  of  the  valley  train,  rises  about  eighty  feet  above  the 
water.  It  may  have  escaped  erosion  by  the  outlet  river  because  of  a 
protecting  ledge  of  bed  rock ;  for  the  rock  rises  in  places  nearly  to  the 
top  of  the  mound.  Joliet  mound,  near  Eockdale,  was  also  an  isolated 
patch  of  the  valley  train,  but  it  has  been  artifically  desti'oyed. 


52  THE   DES  PLAINES  VALLEY.  ]bull.  no.  U 

It  may  be  remarked  here  that  the  four  transverse  sags,  or  passage^, 
across  the  outer  ridge  of  the  Valparaiso  moraine  lie  about  in  line  'with 
four  important  valley  trains  from  the  middle  morainic  belt  (Figs.  1) 
and  10).  The  slough  between  Isle  la  Cache  creek  and  Plainiield  lies 
opposite  the  transverse  valley  of  the  outlet  at  Lemont.  The  slough  at 
the  head  of  Mink  creek  is  nearly  in  line  with  Long  run  at  Romeo.  The 
slough  above  Crystal  run  lies  opposite  Fraction  run,  and  the  tranverse 
valley  of  the  Des  Plaines  at  Brandon's  bridge  is  a  sort  of  continuation 
of  the  united  Hickory  and  Spring  creeks.  While  this  relation  of  valleys 
may  be  purely  accidental,  it  suggests  that  the  position  of  the  main 
rivers  at  the  ice  border  was  not  much  changed  during  the  melting  back 
of  the  ice  front  from  the  west  belt  to  the  middle  belt  of  the  morainr. 

The  east  belt  of  the  morainic  system  is  separated  from  the  middle  belt 
north  of  the  "outlet"  by  the  valley  of  Flag  creek  and  Salt  creek.  At 
Mt.  Forest  island  and  farther  south  its  relation  to  the  middle  belt  is 
more  intimate;  yet  in  places,  especiallly  near  Tinley  park,  the  two 
upland  belts  are  divided  by  a  smooth  plain  of  considerable  width.  The 
contrast  between  the  plain  and  the  rolling  morainic  belts  is  well  seen 
along  the  Eock  Island  railway.  On  Mt.  Forest  island,  east  of  Willow- 
Springs,  the  topography  of  the  moraine  is  unusually  rough.  The  knob.- 
and  hollows  have  a  range  of  over  fifty  feet,  and  ponds  arc  abimdant. 

EXCAVATION  BY  THE  OUTLET  OF  LAKE  CHICAGO. 

Glenwood  stage- — Excavation  of  a  trench  in  the  valley  train. — As  the 
great  lobe  of  the  ice  sheet  melted  back  from  the  Valparaiso  moraine 
there  slowly  opened  up  between  the  moraine  and  the  ice  a  crescent- 
shaped  lake,  known  as  Lake  Chicago  (Fig.  11).  The  waters  of  this  ice- 
dammed  lake  found  their  escape  across  the  moraine  through  the  con- 
verging arms  of  a  V-shaped  depression  which  led  westward  past  Lemont 
and  down  the  broad  longitudinal  valley  between  the  main  ridge  and  the 
outer  ridge  of  the  Valparaiso  morainic  system.  No  precise  reason  can 
be  given  for  the  presence  of  the  two  initial  sags  in  the  moraine  which 
determined  the  two  forks  at  the  upper  end  of  the  outlet,  on  either  side 
of  Mt.  Forest  island.  It-  should  be  recognized,  of  course,  that  accumula- 
tion of  drift  along  the  ice  border  was  quite  irregular,  that  the  moraine 
was  locally  very  weak,  and  that  occasional  transverse  breaks  in  the 
moraines  would  probably  be  maintained  by  the  escape  of  rivers  fed  from 
the  melting  ice.  It  is  clear  that  the  lower  part  of  this  valley,  below 
Lemont,  had  for  some  time  been  occupied  by  a  large  and  much  over- 
loaded glacial  river.  While  the  ice  lingered  at  the  moraine,  the  valley 
had  been  deeply  aggraded  with  gravels,  to  the  altitude  of  about  030 
feet  above  sea  level,  at  Lemont  (Lm.  in  Fig.  10).  The  terraced  remnants 
of  this  old  valley  train  at  certain  places  between  Lemont  and  Joliet 
have  just  been  described.  While  the  valley  train  may  have  had  its 
head  near  Lemont,  in  a  sag  in  the  main  ridge  of  the  Valparaiso  mor- 
aine, it  more  probably  extended  eastward  to  the  vicinity  of  Mt.  Forest, 
where,  during  the  last  stand  of  the  ice  against  the  moraine,  the  escaping 


GOLDTHWAIT]  HISTORY   OF    THE    LOWER    DES  PLAINES. 


53 


Fig.  11.  Two  stages  of  the  glacial  lakes  Chicago  and  Mauniee.  (Leverett  and 
Taylor. )  The  first  might  represent  conditions  in  the  Glenwood  stage ;  the  second 
in  the  Calumet  stage.  Notice  the  expansion  of  the  lakes  northward  as  the  border 
of  the  ice  receded,  and  the  shifting  of  the  outlet  of  Lake  Maumee  from  Fort 
Wayne  to  the  Grand  river,  as  the  lower  pass  was  uncovered  by  the  ice. 


54  THE    DES  PLAINES    VALLEY.  [bull.  no.  U 

waters  would  be  likely  to  maintain  a  tiat-Hoored  valley.  With  the  de- 
velopment of  Lake  Chicago  at  the  head  of  this  valley,  the  character 
of  the  river  was  completely  changed.  The  over-abundant  supply  of 
waste  from  the  melting  ice  was  iioav  carried  into  the  lake  and  left  there. 
The  river  was  thus  relieved  of  its  load,  while  suffering  no  diminution  of 
volume,  so  it  at  once  began  to  gather  up  the  gravels  it  had  previously 
laid  down  and  thu?  to  re-excavate  the  valley. 

A\'hile  Lake  Chicago  was  extending  itself  northward,  as  the  edge  of 
the  ice  retreated  (Fig  11)  its  outlet  was  cutting  a  wide  trench  iu  the 
valley  train,  and  so  slowly  lowering  the  level  of  the  lake.  (This  is  shown 
in  profile,  in  Fig.  12).  Along  the  shore  of  the  lake  at  this  time  waves 
and  currents  were  busily  cutting  terraces  and  building  beaches  like  those 
of  the  present  shore,  at  a  height 'which  indicates  that  the  water  stood 
about  fifty-five  feet  above  the  present  Lake  Michigan.  The  common 
occurrence  of  a  set  of  parallel  beaches  whose  crest  altitudes  range  from 

55  down  to  50  feet  above  the  present  lake  doubtless  shows  that  the  lake 
level  was  not  exactly  stationary,  but  was  falling  slowly  as  the  out- 
flowing river  deepened  its  channel.  This  earliest  and  highest  stage 
of  Lake  Chicago  has  been  named  the  "Glenwood"  stage,  because  it^ 
shoreline  is  very  conspicuous  near  Glenwood,  Illinois. 

Calumet  stage — llie  Lockport  sill. — We  may  get  further  light  on  the 
history  of  the  outlet  from  the  lower  beaches  of  this  extinct  lake.  About 
twenty  feet  lower  than  the  Glenwood  shoreline,  in  the  Chicago  district, 
is  a  strongly  developed  beach  called  the  ■'"Calumet"  shoreline.  It  marks 
a  stage  when  the  lake  stood  for  a  considerable  time  at  the  height  of 
30  or  35  feet  above  its  present  level.  Below  the  Calumet  beach  is  a  group 
of  shorelines,  called  the  Toleston  shorelines  (from  the  town  of  Toleston, 
Indiana.)  This  includes  a  well  defined  beach,  20-25  feet  above  Lake 
Michigan,  and  a  series  of  closely  set  ridges  from  16  feet  above  the  lake 
down  to  its  level,  which  represents  stages  when  the  lake  was  falling  from 
the  Toleston  level  to  that  of  the  present  Lake  Michigan.  Evidently  the 
surface  of  Lake  Chicago  was  not  lowered  steadily  and  uniformly  from 
the  55-foot  mark  to  the  level  of  Lake  Michigan,,  but  went  on  inter- 
ruptedly, halting  for  a  considerable  time  at  the  35-foot  level,  then 
falling  rather  suddenly  to  20  feet,  and  then  by  several  successive  lower- 
ings  gaining  its  present  level. 

Eeasons  for  these  spasmodic  changes  in  level  seem  to  exist  in  the 
way  the  Chicago  outlet  was  deepened.  As  the  river  cut  down  farther  and 
farther  through  the  gravels,  it  seems  to  have  encountered  a  ledge  of 
bed  rock  at  Lockport,  (Fig.  12,  a.  &  c),  at  a  height  of  hardly  30  feet 
above  Lake  Michigan.  Downward  cutting  of  the  vallev  floor  was  at  once 
arrested,  while  the  surface  of  the  rock  was  widely  stripped  of  its  cover- 
ing of  drift  and  gravels.  What  seem  to  be  remnants  of  this  old  rock 
floor  or  sill,  which  was  formerly  continuous  across  the  valley,  are  flat 
topped  terraces  of  rock  in  the  village  of  Lockport  and  at  a  corresponding 
height  on  the  west  side  of  the  valley  near  the  Sprague  school  house.  The 
surface  of  the  rock  terrace  at  Lockport  is  30  feet  above  Lake  Michigan. 
While  the  lake  stood  at  the  3o-foot  level,  therefore,  the  depth  of  the 


GOLDTHWAIT.]  HISTORY    OF    THE    LOWER    DES  PIAINES.  00 

ancient  river,  close  to  its  left  bank,  at  Lockport,  was  not  more  than  fiv^ 
feet.  It  seems  probable  that  the  surface  of  the  rock  sill  (if  one  existed 
there)  was  lower  than  this  near  the  center  of  the  valley,  and  the  river 
deeper  than  five  feet  there.  On  the  basis  of  this  supposed  sill  it  is  not 
hard  to  explain  the  manner  in  which  it  was  worn  thro  jgh  so  as  to  cause 
a  sudden  drop  in  level  of  Lake  Chicago.  It  would  be  natural  for  rapids 
to  be  established  on  the  down-valley  side  of  the  sill,  (at  a  in  Fig.  12) 
perhaps  near  the  head  of  Joliet  pool,  where  the  river  passed  from  the 
hard  Niagara  limestone  to  the  softer  limestones  and  shales  of  the  Cin- 
cinnati formation.  Meanwhile  on  the  up-valley  side  of  the  sill  at 
Lockport,  the  river  would  be  unable  to  cut  its  drift  floor  below  the 
30-foot  level,  and  the  lake  would  conseciuently  be  held  at  a  level  a  few 
feet  above  the  channel  floor,  or  about  35  feet,  while  the  rapids  on  the 
lower  side  of  the  sill  would  be  wearing  backward  past  Joliet  (towards 
0  and  c  in  Fig.  12.)  Had  the  I^^iagara  limestone  been  less  massive 
and  uniform  in  structure,  falls  instead  of  rapids  might  have  been  de- 
veloped, leaving,  by  their  recession,  a  sharply  defined  gorge  like  that 
below  Niagara  Falls;  but  the  structure  of  the  rock  at  Joliet  and  Lock- 
port  probably  did  not  permit  this.     Where   the   rapids  were   swift,  a 


^"/ii''   ^      ■„    ^^^  Lak&       Chicago 

^Moraine.      ^  ,        -^ 

~  S  t  e  o  >v  o  o  cL  sToge 


Fig.  12.  Diagram  showing  liow  tlie  removal  of  a  sill  of  bed  rock  in  the  Chicago 
outlet,  by  "stoping,"  may  have  caused  the  sudden  drop  in  level  of  the  lake  from 
the    Calumet   to    the    Toleston. 

steep,  straight  bluff  of  rock  was  left  facing  the  valley.  Tlais  seems  io 
liave  l^een  tlie  origin  of  the  high  bliff  on  the  west  side  of  the  river  at 
Joliet,  between  Exchange  street  and  Theiler's  park,  and  on  the  east  side- 
at  Lockport,  from  Dellwood  park  to  the  north  end  of  the  village.  For 
the  greater  part  of  the  course,  however,  no  striking  gorge  was  pro- 
duced. As  the  rapids  receded  up  the  valley  towards  Lockport,  the 
distance  across  the  sill  became  shorter  and  shorter.  A  sudden  change 
followed  when  the  rapids  arrived  at  the  very  head  of  the  sill  (c  in  Fig. 
12)  and  the  last  of  the  controlling  ledge  was  removed.  The  drift 
floor  above  Lockport  was  degraded  at  once  some  15  feet,  down  to  the 
lower  rock  floor,  and  the  surface  of  Lake  Chicago  fell  correspondingly 
to  the  "Toleston"  level.  While  the  removal  of  the  barrier  and  the 
fall  of  the  lake  should  of  course  not  be  thought  of  as  instantaneous,  it 
would  be  sudden  compared  to  the  long  time  it  would  take  fo^  the 
rapids  to  eat  back  through  the  sill  (from  a  to  c)  a  distance  of  perhaps 
four  or  five  times.  It  might  well  have  caused  the  lake  to  drop  so 
promptly  from  the  level  35  feet  above  the  present  lake  to  a  level  20 
feet  above  it  that  no  beaches  were  built  between  the  Cal  imet  and  the 
Toleston. 

Toleston  and  later  stages — Abandonment  of  the  outlet,  and  suhsti- 
iuliou  of  the  Des  Plaines  river. — In  the  course  of  time  the  border  of 


56  THE    DES  PLAINES    VALLEY.  bili.  no.  11  1 

the  ice  withdrew  northward  j^ast  the  low  region  at  the  head  of  Little 
Traverse  bay  and  past  the  Straits  of  Mackinaw,  and  Lake  Cliicago 
inei-o-ed  witli  a  larger  lake,  Lake  Algonquin,  which  then  occupied  the 
Huron  l)asin.  Although  the  history  of  this  lake  has  not  been  fully 
worked  out,  it  seems  probable  that  at  the  time  the  waters  of  the  Mich- 
igan basin  became  a  part  of  it, -Lake  Algonquin  stood  at  a  very  low 
level,  discharging  eastward  through  the  valley  of  the  Trent  river  near 
Kirkfield,  Ontario.  That  region  then  stood  much  lower  than  now,  and 
the  surface  of  I^ake  Algonquin  at  that  stage  was  probably  considerably 
below  the  present  level  of  Lake  Huron  and  Lake  Michigan.  This  low 
water  stage  was  only  a  short  one,  however,  for  the  northern  part  of  the 
Great  Lake  region,  including  the  Trent  O-itlet,  was  soon  raised,  until 
the  discharge  of  Lake  Algonquin  had  been  shifted  to  the  St.  Clair 
river  at  Port  Huron.  This  brought  tlie  surface  of  the  waters  in  the 
Lake  jMichigan  basin  up  to  al)out  1'2  feet  above  the  present  level.  Tbe 
series  of  changes  which  beset  Lake  Algonquin  after  this,  as  the  ice  re- 
ceded and  as  earth  movements  warped  the  northern  part  of  the  sur- 
rounding region,  are  complex,  and  have  not  yet  been  fully  worked  out. 
It  is  enough  hero  to  remark  that  the  waters  in  the  Micliigui 
basin  remained  long  at  the  l'?-foot  level,  returning  to  it  after  a  second 
stage  of  low  water  that  was  probably  even  lower  than  the  first  had  been. 
This  was  brought  about  by  the  uncovering  of  the  "Nipissing"  pass, 
east  of  Xorth  Bay,  Ontario,  which  at  that  time  stood  very  close  to  sea 
level,  and  by  the  subsequent  uplift  of  that  region  and  re-establishment 
of  the  outlet  at  Port  Huron.  At  some  time  during  these  recurrent 
12-foot  stages  of  Lake  Algonquin  and  the  Xipissing  great  lakes,  the 
shallow  Chicago  outlet  was  shut  off  by  a  long  reef  of  sand  which  can 
be  traced  through  the  Chicago  district  from  Lincoln  park  to  South 
Engiewood.  The  discharge  of  Lake  Algonquin  and  of  its  successors, 
the  Nipissing  great  lakes,  came  in  this  way  to  be  concentrated  at  Port 
Huron,  where  the  outflow  was  across  glacial  drift  instead  of  across 
hard  rock. 

Thus  the  Chicago  outlet  was  abandoned.  In  place  of  the  great  river 
whose  volume  was  perhaps  comparable  to  that  of  the  St.  Clair  river 
today,  was  left  the  little  Des  Plaines,  a  stranger  in  the  district,  which 
straggled  into  the  great  valley  as  if  by  accident.  Extending  its  mouth 
out  on  the  flat  plain  south  of  Riverside  as  the  lake  fell  and  its  shore 
moved  eastward,  the  Des  Plaines  seems  almost  to  have  had  a  free  choice 
bet\^ieen  a  course  to  the  Mississippi  or  to  the  St.  Lawrence.  During 
floods,  if  not  at  ordinary  stages,  the  river  used  to  discharge  a  part  of 
its  volume  eastward  to  the  south  branch  of  the  Chicago  river.  The 
slougli.  "Mud  lake,"  (See  Fig.  19),  which  marks  the  old  channel,  may 
for  a  time  have  carried  the  entire  river  out  towards  Lake  Michigan. 
What  caused  the  channel  to  silt  up  and  the  river  to  turn  westward  near 
Summit  is  not  known.  Perhaps,  as  Mr.  L.  E.  Cooley,  consulting  en- 
gineer of  the  Internal  Improvement  Commission,  has  suggested,  a  small 
colony  of  industrious  beavers,  building  a  beaver-dam,  were  responsible. 
Whatever  the  reason,  the  Des  Plaines  finally  found  its  way  westward  ; 
and  as  a  result  the  valley  of  the  extinct  outlet  has  not  been  left  whoHv 


GOLDTHWAIT.J  HISTORY    OF   THE    LOWER    DES  PLAINES.  57 

unoccupied  by  drainage,  but  serves  as  a  valley  for  a  river  several 
sizes  too  small  for  it.  At  Eomeo,  large  pot-holes  in  the  rock  floor  of 
the  valley  near  the  Des  Plaines  river  tell  the  story  of  the  deeper  and 
more  powerful  river  of  ancient  times. 

The  amount  of  erosion  that  the  Des  Plaines  has  accomplished  in  its 
straggling  course  on  the  valley  floor  is  very  slight.  Even  between 
Eomeo  and  Joliet,  where  the  steeper  grade  of  the  rock  floor  produces 
rapids  in  the  river,  its  channel  is  low  and  ill-defined.  Expanding  and 
contracting  as  it  enters  and  leaves  shallow  hollows  on  the  outlet  of  the 
floor,  branching  and  uniting  about  low  islands  which  are  not  bars  of  its 
own  construction,  turning  to  right  and  left  in  its  course  down  the 
valley,  yet  at  no  place  (above  Jbliet)  approaching  near  enough  to  under- 
cut the  bluffs  as  they  must  once  have  l)een  undercut,  and  occupying 
usually  less  than  one-tenth  of  the  width  of  the  valley,  the  Des  Plaines 
is  manifestly  an  incompetent  river.  The  valley  it  follows  is  not  its  own, 
but  one  -^vhich  it  inherited. 

EROSION  BY  TRIBUTARIES. 

Fraciion  run. — It  is  interesting  to  see  what  the  tributary  streams  were 
accomplishing  while  the  great  outlet  was  being  excavated.  As  an  ex- 
ample of  tributaries  which  enter  the  outlet  midway  of  the  supposed  rock 
sill,  we  mav  take  Fraction  run,  which  joins  the  Des  Plaines  between 
Lockport  and  Joliet.  Like  the  main  valley,  this  tributary  was  ag- 
graded with  gravels  while  the  ice  lay  against  the  Valparaiso  moraine. 
Pemnants  of  a  smooth-topped  valley  train  remain  in  terraces  on  either 
side  of  Fraction  run,  in  and  above  Dellwood  park.  The  Chautauqua 
building  stands  on  this  terrace.  Beyond  the  park  fence,  a  short  dis- 
tance up-stream,  broader  and  better  remnants  of  the  outwash  terrace, 
with  gravelly  constitution,  are  to  be  seen  on  both  sides  of  the  run,  at 
a  height  of  15  feet  above  the  present  valley  floor. 

During  the  Glenwood  stage  of  Lake  Chicago,  while  the  ancestral 
river  lowered  its  channel  in  the  gravels  down  to  the  surface  of  the 
rock  sill,  its  little  tributary  did  the  same.  Fragments  of  the  outwash 
were  left  as  terraces  standing  above  the  rock  floor  of  the  run.  While 
the  rapids  on  the  down-valley  side  of  the  Lockport  sill  were  receding 
northward  from  Joliet  towards  Fraction  run,  the  small  side  stream  was 
adjusted  to  the  level  of  the  sill  at  its  mouth;  but  as  the  rapids  migrated 
up  the  main  valley  past  the  mouth  of  the  tributary  the  side  stream 
suddenly  found  itself  tumbling  over  the  face  of  a  gorge,  the  perpen- 
dicular wall  of  rock  which  overlooks  the  old  canal  near  the  entrance  to 
Dellwood  park.  The  diagram.  Fig  13,  illustrates  this  process.  The 
waterfall  thus  given  to  Fraction  run  must  soon  have  been  reduced  to 
a  series  of  rapids,  for  limestone  of  so  uniform  a  structure,  would  not 
permit  falls  to  be  long  maintained.  By  the  recession  of  the  rapids  up 
the  run,  a  steep-walled  gorge  was  cut  in  the  rock.  At  its  mouth  the 
gorge  is  equal  in  depth  to  the  cliff  cut  by  the  main  river  in  the  sill, 
but  toward  the  head  of  the  gorge  its  depth  decreases.  Where  so  coarse 
a  load  is  gathered  and  must  be  carried  by  the  stream,  it  is  forced  to 


58 


THE    DES  PLAINES   VALLEY. 


[BULL.  NO.  11 


maintain  a  steeper  slope  than  that  of  the  old  bed  rock  surface.  In 
the  park  the  bed  of  the  stream  has  been  obscured  by  the  construction 
of  two  dams  to  form  artificial  ponds.  Near  the  high  cement  bridge 
the  gorge  is  cut  about  20  feet  deep  in  rock.  The  limestone  there  is  thin- 
bedded,  cherty,  and  very  much  cracked  hy  joint  planes.  Just  above  the 
bridge,  near  ithe  upper  dam  and  the  trestle  of  the  scenic  railway,  is  a 
fine  natural  exposure  of  the  limestone,  coated  with  lichens.  The  over- 
hanging cliff  is  due  to  a  slightly  inclined  joint  crack.  The  strata  dip 
10°  to  15°  toward  the  southwest,  witli  local  warpings.     One  may  see 


Fig.  13.  Diagram  illu-'^trating  the  way  in  which  the  up-river  valley  migration 
of  falls  or  rapids  on  a  river  affects  its  tributaries.  The  falls  ha\e  been  worn  back 
from  near  the  front  of  the  diagram  past  tributaries  a  and  b.  and  are  now -ap- 
proaching c.  When  tliey  pass  c.  the  mouth  of  the  side  stream  will  be  suddenly 
lowered  from  the  level  of  the  crest  of  the  falls  to  that  of  the  base,  forming  a  fall 
or  rapids  there.  This  has  just  occurred  at  b.  These  falls  or  rapids  will  then  re- 
cede up  the  side  valley,  forming  a  branch  gorge.  This  stage  in  the  process  has 
just  been  reached  at  ft,  but  has  been  passed  at  a. 

here  the  way  in  which  the  much  jointed  rock  on  the  cliff  face  is  wedged 
and  loosened  by  frost  and  decay,  falling,  piece  by  piece,  into  the  stream. 
Should  the  process  seem  too  slow  to  account  for  the  sculpturing  of  the 
gorge,  we  must  remember  that  the  age  of  the  gorge  is  to  be  measured, 
not  in  tens,  but  in  thousands  of  years. 

Farther  up  the  run,  beyond  the  park  fence,  one  may  see  in  its  natural 
condition  the  rocky  channel  of  the  stream  at  the  shallow  head  of  its 
gorge.  A  long  string  of  riffles  and  pools  formed  by  the  step-like  bedding 
planes  illustrates  remarkably  well,  though  on  a  small  scale,  the  un- 
graded condition  of  a  young  stream.     Here  also  is  a  precipitous  60-foot 


GOLDTHWAIT].  HISTORY   OF    THE    LOWER    DES  PLAINES.  59 

bluff,  where  the  run  has  swung  against  the  north  side  of  its  valley,  de- 
stroying the  outwash  terrace  and  trimming  back  the  moraine  and  the 
underlying  rock  (See  Plate  5,  B.)  The  valley  floor  above  the  park  i> 
broad  and  flat,  built  of  loose  rubble  which  the  stream  has  torn  from  its 
banks.  It  appear  to  have  been  the  flood  plain  of  the  creek  when  it  was 
adjusted  to  the  level  of  the  rock  sill,  and  to  have  been  only  slightly 
trenched  by  the  channel  since  the  development  and  headward  extension 
of  the  rapids  up  the  run.  Opposite  the  high  bluff,  on  the  south  side 
of  the  valley,  a  broad  flat  remnant  of  the  outwash  terrace,  15  feet  above 
the  present  valley  floor,  runs  from  the  northeast  corner  of  the  park  up- 
stream several  himdred  yards,  and  there  finds  continuation  in  a  broader 
terrace  on  the  north  side  of  the  valley. 

Long  run  and  other  tributaries  above  the  sill. — Two  sets  of  terraces 
occur  along  the  run.  The  higher  is  an  outwash  or  valley-train  terrace, 
to  be  correlated  with  the  Glenwood  stage  of  La;ke  Chicago,  and  the 
lower  one  is  a  terrace  adjusted  to  the  rock  sill  at  Lockport,  contem- 
poraneous with  the  Calumet  stage  of  the  lake.  Where  Long  run  enters 
the  main  valley,  a  mile  south  of  Eomeo,  the  two  terraces  alluded  to 
may  be  seen  from  the  trolley  car.  The  outwash  terrace  is  about  30 
and  the  lower  terrace,  12  feet  above  the  creek. 

Other  tributary  ravines  which  enter  the  upper  portion  of  the  outlet 
between  Willow  Springs  and  Lemont,  sometimes  show  two  terraces. 
One  of  these  is  a  large  ravine  a  mile  and  a  half  east  of  Lemont  (in 
sections  22  and  27,  Lemont  township).  The  two  terraces  appear  near 
the  mouth  of  the  ravine,  in  plain  sight  of  the  road  that  runs  south 
from  the  school  house.  The  higher  stands  about  30  feet  above  the 
present  flood  plain  and  the  lower  15  feet  above  it.  Only  a  few  remnants 
of  the  higher  one  remain,  but  the  lower  one  may  be  followed  inter- 
ruptedly far  np  the  valley,  where  the  present  flood  plain  gradually 
rises  to  meet  it.  Judging  from  the  interval  between  the  old  flood  plain 
remnants  and  the  present  floor  of  the  ravine,  near  the  main  outlet,  the 
higher  terrace  corresponds  with  the  Glenwood  and  the  lower  with  the 
Calumet  stage. 

Eavines  cut  by  streams  which  entered  Lake  Chicago  along  the  north 
shore  at  Glencoe,  Waukegan,  and  Zion  City,  show  terraces  at  the  same 
height  as  the  ravines  which  entered  the  outlet  above  Lockport.  They 
obviously  mark  repeated  lowerings  of  the  lake,  which  correspond  with 
repeated  deepenings  of  the  river.^ 

Spring  creeh  and  HicTcory  creek. — Both  Spring  creek  and  Hickory 
creek  were  aggraded  with  valley  trains,  like  Long  run;  and  since  they 
are  larger  streams  they  have  even  more  conspicuous  outwash  terraces 
than  it  has.  The  lower  terrace  seems  to  be  absent  here,  however,  this 
suggests  that  these  creeks  may  have  joined  the  main  river  below  the 
iLockport  sill,  so  did  not  have  to  adjust  their  floors  to  a  temporary 
rock  barrier. 


1  For  a  description  of  these  ravines,  and  a  discussion  of  their  significance,  see 
BuU.  7  of  the  111.  Geol.  Surv.,  on  the  "Physiography  of  the  Evanston-Waulcegan 
District,"   by  W.   W.  Atwood  and  J.   W.   Goldthwait,   pp.   69-84.      1908. 


60  THE    DES  PLAINES    VALLEY.  IBDLL.  NO.  11 

.Sugar  creel-. — Unlike  tlie  other  tributaries  near  Joliet,  Sugar  creek 
has  had  to  cut  down  its  channel  in  bed  rock;  for  the  Niagara  limestone 
there  rises  higher  than  on  Hickory  creek. 

Accordingly,  it  has  worn  out  a  narrow  gorge  in  the  flat-bedded  lime- 
stone from  the  Chicago  &  Alton  railway  bridge  down  to  the  slaughter 
house  road,  near  the  old  tin-plate  mill  (See  the  map  of  this  gorge. 
Plate  6.)  The  gorge  is  nearly  15  feet  deep,  with  vertical  cliffs  cut  out 
along  joint  cracks  and  a  rock  floor  broken  by  a  long  succession  of  little 
rapids,  where  the  edges  of  the  harder,  cherty  beds  offer  greater  resistance 
to  erosion.  These  little  water-falls  (for  such  they  are,  except  when 
the  stream  is  flooded)  frequently  cross  the  gorge;  not  in  a  straight 
line,  but  in  a  cirve,  which  is  concave  down  stream  on  account  of  the 
more  rapid  recession  in  the  middle,  where  the  current  is  faster  than 
at  the  sides.  In  this  regard  they  imitate  the  great  Horeshoe  falls  of 
Niagara,  which,  as  it  happens,  plunge  over  tlie  very  same  limestone  form- 
ation. In  the  pools  between  the  rapids,  one  may  see  in  low  water  the 
chipstone  waste  that  is  being  swept  down  stream  during  each  flood. 
The  discoidal  or  tabular  blocks  and  pebbles  (even  the  larger  slabs  which 
have  been  banlced  up  by  the  boys  to  form  a  swimming  pool,  and  then 
moved  by  the  creek,  in  floods)  lie  packed  like  the  overlapping  shingles 
on  a  roof,  slanting  up  stream.  The  shingle  structure  is  even  more  im- 
pressively shown  on  Hickory  creek,  below  the  old  red  mill,  where  the 
freshet  of  February,  1907,  scattered  large  tabular  slabs  and  chips  of 
rock  far  and  wide  over  the  flood-plain. 

The  jointed  walls  of  the  gorge  of  Sugar  creek  offer  favorable  op- 
portunity to  study  the  manner  in  which  joints  aid  or  direct  stream 
erosion  along  definite  lines.  The  bare  walls,  faced  by  joints,  permit  no 
doubt  as  to  the  advantage  taken  by  the  stream  to  tear  away  the  limestone, 
block  by  block,  as  the  workman  does  in  quarrying.  At  the  same  time, 
it  is  clear  from  the  course  of  the  creek,  which  runs  oblique  to  the  two 
master  systems  of  joints  in  such  a  way  that  the  walls  of  the  gorge  have 
a  zigzag,  rather  than  a  straight  course,  that  while  joints  aid  the  stream 
they  may  not  direct  its  work  along  definite  lines.  Instead  of  running 
parallel  to  either  of  the  two  prominent  sets  of  joints,  the  gorge  of  Sugar 
creek  bisects  the  angle  between  them.  On  the  map,  where  the  direc- 
tion of  the  joints  near  the  gorge  is  shown  by  a  symbol,  the  discordance 
between  the  joints  and  the  trend  of  the  stream  comes  out  plainly. 

Feed's  woods  ravine. — One  of  the  prettiest  and  most  instructive  ex- 
amples of  excavation  by  a  tributary  in  the  glacial  drift  is  the  ravine 
in  Reed's  woods,  above  Bush  park  (See  Plate  7).  There  are  several 
features  to  be  observed  here  which,  taken  together,  cannot  fail  to  con- 
vince one  that  this  deep  ravine  and  its  tributaries  have  been  carved  out 
wholly  by  the  activity  of  rain  and  running  water. 

In  the  first  place,  the  behavior  of  the  creek  and  its  little  tributaries 
during  wet  weather  is  significant.  The  main  channel  at  such  times  may 
be  filled  brim  full  or  even  to  overflowing,  so  that  the  little  flood-plain 
which  forms  the  floor  of  the  valley  is  under  water.  In  its  swollen  con- 
dition the  stream  may  be  seen  to  carrv  fine  sediment  in  suspension  and 
to  roll  sand  and  fine  gravel  alonsr  the  bed  of  the  channel.     Around  the 


GOLDTHWAIT.]  HISTOKY    OF    THE    LOWEK   DES  PLAINES.  61 

outside  of  every  sharp  curve — and  there  are  many  such — the  stream 
has  cut  away  its  bank.  At  points  where  the  channel  swings  against 
one  side  of  the  valley,  bare  slopes  of  glacial  drift  may  be  seen,  several 
feet  high  and  very  steep.  After  a  rain  it  is  not  unusual  to  iind  little 
pillars  of  clay,  capped  by  pebbles  or  other  protective  objects,  around 
which  the  rain  has  excavated  the  fine  cla3^  Obviously,  with  the  wash- 
ing away  of  soil  from  exposed  side  slopes  and  from  the  channel  bank 
the  ravine  is  changing  form,  be  it  ever  so  slowly. 

Material  thus  obtained  is  washed  into  the  stream  and  swept  down- 
valley  (except  such  large  pebbles  and  bowlders  as  cannot  be  moved), 
to  be  deposited  sooner  or  later  in  the  channel  on  the  inside  of  some 
curve,  often  directly  opposite  a  place  where  cutting  of  the  outer  bank 
is  going  on.  It  is  by  this  "cut-and-filP  process  that  the  flood-plain  hns 
been  built,  for  even  now  it  is  being  broadened  by  the  extension  of  de- 
posits on  the  one  side  and  by  lateral  erosion  on  the  other,  at  those  points 
where  the  channel  swings  to  the  extreme  border  of  the  floor.  In  the 
freshly  exposed  channel  in  dry  weather  may  be  seen  the  stratified  struc- 
ture of  the  flood-plain,  due  to  its  having  been  built  up  under  water  by 
sediment  transported  by  the  stream.  Each  variation  in  volume  of  the 
stream  means  a  variation  in  its  carrying  power;  hence  it  is  repeatedly 
depositing  a  layer  of  different  texture  from  the  preceding  layers.  The 
surface  of  the  flood-plain  is,  indeed,  merely  a  part  of  the  waste  material 
that  is  gathered  up  by  the  creek  and  its  wet  weather  branches  and  is 
just  now  on  its  way  down  to  the  valley  of  the  Des  Plaines.  'Not  only 
will  the  stream  gather  sediment  from  either  side.  l)iit  it  will  pick  up 
material  from  the  bed  of  its  channel  d.iring  each  flood,  and  the  channel 
floor  will  be  lowered  thereby.  Judging  from  the  rate  at  which  the 
waste  is  moving  down  the  fllood-plain-path — a  slow  rate,  to  be  sure,  oper- 
ative only  in  wet  weather,  yet  a  perceptible  one — we  may  believe  that  in 
the  thousands  or  tens  of  thousands  of  years  during  which  the  drift  has 
been  exposed  to  running  water,  a  ravine  as  large  as  this  has  been  exca- 
vated. The  process  of  transportation  must  needs  involve  excavation.  The 
ravine,  then,  is  constantly  growing  deeper  as  the  stream  cuts  dovv^nward 
along  its  bed,  and  wider  as  the  stream  planes  away  the  border  of  its 
flood-plain,  and  rain  washes  down  the  side  slopes. 

In  this  connection  it  is  worth  while  to  consider  the  effect  which  exca- 
vation has  at  the  head  ol  a  ravine.  Examine,  for  instance,  the  ex- 
treme upper  end  of  some  little  side  ravine  or  gully  (selecting,  of  course, 
one  in  which  the  natural  conditions  have  not  been  upset  by  artificial 
drains  or  rubbish  heaps.)  The  one  in  Plate  8,  A,  for  instance,  is  a 
straight,  steep-sided  gully,  usually  withoit  sod,  exhibiting  the  sharp 
outlines  of  a  recently  rain-cut  surface.  When  it  rains,  the  water  which 
falls  in  this  gully  and  that  which  is  shed  into  it  cuts  down  its  steeply 
inclined  bed  and  thereby  cuts  back  its  head.  The  deepening  and  the 
headward  growth  of  such  a  gully  are  inseparable.  Thus,  while  the  water 
is  running  from  the  head  toward  the  mouth  of  a  stream,  the  stream 
valley  and,  consequently,  the  stream  itself,  wear  headward,  or,  as  it 
might  seem,  backward.  The  exact  direction  in  which  the  gully  works 
back  is  determined  partly  by   inequalities  of  surface  slope — for  a   de- 


(i2 


THE    DES  PLAINER    VALLEY. 


[BULL.   NO.   11 


pre?sion  which  concentrates  the  run-off  and  delivers  it  to  the  gully  will 
cause  the  gully  to  lengthen  in  that  direction;  and  partly  by  inequalities 
in  structure  of  the  ground,  for  if  hard  and  soft  materials  lie  side  by 
side,  the  running  water  will  select  a  path  along  the  soft  belt.  Even 
foreign  obstruction  like  tree  roots  or  large  bowlders  serve  to  turn  a 
young  valley  to  one  side,  and  perhaps  wholly  change  its  future  course 
of  growth.  Here  tlien,  at  the  extreme  head  of  a  ravine,  we  may  see 
the  work  of  excavation  in  its  infantile  stages.  The  difference  between 
the  head-water  gully  and  the  full  grown  main  ravine,  is  one  not  of  kind, 
but  of  size.  This  stream  has  only  recently  worked  back  to  the  gully 
head,  and  there  its  volume  is  exceedingly  small;  consequently  very  little 
excavation  has  been  accomplished.  The  main  ravine,  however,"  began 
long  ago  to  be  cut  out  by  the  growing  stream,  and  with  its  growth  the 
size  and  power  of  the  stream  has  been  increased  at  a  more  and  more 
rapid  rate. 

Another  feature  that  demands  attention  is  the  straightness  of  the 
j-oung  gully.     It  is  a  matter  of  easy  observation  that  an  enlarged  gullv 


Fig.   14.     A  crooked  guUy  in  an  early  stage  of  development. 

or  small  ravine  like  the  one  which  enters  Rush  creek  from  the  north 
in  the  center  of  Eeed's  woods  (See  Plate  7),  follows  a  crooked  path 
on  its  way  down  to  the  main  ravine,  bending  back  and  forth  between 
a  series  of  projecting  spurs.  Where  developed  under  favorable  con- 
ditions, these  bends  may  be  exceedingly  symmetrical  and  evenly  spaced. 
Careful  inspection  and  legitimate  reasoning  show  that  they  represent 
irregularities  or  crooks  in  the  incipient  gully  which  have  been  enlarged 
and  modified  until  they  approach  conventional  curves  as  small  acci- 
dental obstructions  become  less  and  less  effective  and  the  minor  crooks 


GOLDTHWAIT.J 


HISTORY   OF    THE    LOWER    DES  PLAINES. 


68 


are  eliminated  (See  Figures  14  aud  15.)  While  the  curves  which  survive 
in  this  gi'owth  are  slowly  enlarged  by  outward  cutting,  they  begin  to 
shift  distinctly  down-valley.  The  exi^lanation  of  this  lies  in  the  fact 
that  wherever  a  stream  winds  around  a  spur  it  cuts  a  little  more  strongly 
against  the  ui>valley  side  of  that  spur  than  on  the  down-valley  side  of 
the  spur  next  above.  Thus,  while  the  stream  curves  push  their  way 
slowly  down-valley,  and  the  spurs  are  slowly  consumed  by  the  trimming 
away  of  their  up-valley  sides,  the  valley  itself  is  widened,  and  soon  the 
beginnings  of  a  flood-plain  may  be,  seen.  The  main  ravine  (that  of 
Bush  creek  on  the  map,  Plate  7)  has  passed  through  exactly  these 
stages  of  growth.  It  has  not  only  been  deepened  25  feet  below  the 
iipland  level,  but  by  the  lateral  swinging  of  the  creek  it  has  been 
widejied  about  150  feet.  At  the  same  time,  by  the  down-valley  shifting 
of  its  curves,  the  original  spurs  have  been  half  trimmed  away.    The  map 


Fig.  15.  Same  guUy  as  in  Fig.  14,  in  a  later  stage.  As  the  gully  has  been 
deepened  by  the  growing  stream,  the  crooks  and  bends  have  become  larger  and 
more  conventional.  A  series  of  overlapping  spurs  has  been  formed.  On  the  outside 
of  each  curve  and  the  up-valley  side  of  each  spur  the  stream  is  actively  trimming 
its  bank.  On  the  inside  of  each  curve  and  the  down-valley  side  of  each  spur  it  is 
building  a  flood  plain. 

shows  plainly  the  maimer  in  which  the  creek  is  attacking  the  up- 
vallev  side  of  three  half -consumed  spurs  in  Eeed's  woods.  Obviously 
this  "is  not  an  accidental  but  a  systematic  relation.  At  these  points 
the  steep  bank  of  the  ravine  is  bare  where  the  stream  has  recently  been 
undermining  it.  Perhaps  a  tree  leaning  over  the  creek  at  a  precarious 
angle  tells  the  same  story  of  the  continued  activity.  What  better  ex- 
planation for  these  phenomena  than  that  the  ravine  is  being  and  has 
iDeen  cut  out  by  the  creek  ?  How  else,  indeed,  can  such  a  group  of  facts 
be  accounted  for?  If  there  should  still  be  doibt  regarding  the  ability 
of  so  small  a  creek  to  excavate  so  large  a  ravine,  we  must  consider  the 


64  THE    DES  PLAINES   VALLEY.  [BULL.  no.  U 

statement  of  an  old-time  Scotch  gGologipt,  John  Playfair.  who.  calling 
attention  to  the  manner  in  which  side  valleys  of  a  river  system  join 
the  main  valley,  declared,  in  1802,  that  side  valleys  have  "such  a  nice 
adjustment  of  their  declivities  that  none  of  them  join  the  principal 
valley  either  on  two  high  or  too  low  a  level ;  a  circumstance  which  would 
be  infinitely  improbable  if  each  of  these  vallies  were  not  the  work  of  the 
stream  that  flows  in  it/'^ 

This  feature,  as  well  as  the  others,  is  illustrated  in  the  Bush  creek 
ravine.  They  are  not  "ready  made"  valleys;  fashioned  for  the  streams; 
they  have  been  slowly  and  laboriously  cut  out  by  the  streams  themselves, 
and  testify  to  the  changes  which  can  be  wrought  out  in  long  periods 
of  time.  This  creek,  it  might  be  remarked,  is  probably  some  thousiuds 
or  tens  of  thousands  of  years  old.  ' 

Before  leaving  this  ravine  a  few  minor  points  should  not  be  over- 
looked. The  process  of  downward  excavation  seems  to  have  been  ar- 
rested at  least  once;  for  there  are  fragments  of  the  old  valley  floor  now 
in  the  form  of  terraces,  on  the  down-valley  side  of  spurs,  at  a  height  of 
about  eight  feet  above  the  present  flood-plain.  Whether  this  terrace 
corresponds  to  the  stage  when  the  Des  Plaines  valley  was  aggraded  with 
the  valley  train  or  to  some  subsequent  stage  of  temporary  interruption 
of  the  process  of  excavation  cannot  confidently  be  told.  The  amount 
of  work  accomplished  by  the  creek  in  cutting  down  to  the  level  of  tlio 
terrace  seems  to  indicate  a  later  stage  than  that  of  the  outwash  filling. 
If  so,  either  the  Lockport  sill  extended  down-valley  as  far  as  the  mouth 
of  the  creek,  or  there  was  some  other  obstruction  in  the  valley  to  hold 
the  tributary  for  a  time  near  a  local  base  level.  The  presence  of  ter- 
races at  various  levels  around  the  base  of  Flathead  mound,  a  few  miles 
farther  down  the  Des  Plaines  valley,  suggests  that  even  down  beyond 
the  Lockport  sill  the  old  outlet  of  Lake  Chicago  reduced  its  channel 
by  successive  stages.  Another  small  feature  of  the  basin  in  the  Bush 
creek  ravine  is  an  outcrop  of  cemented  gravel,  or  conglomerate,  in  the 
bed  of  the  creek,  where  it  is  cutting  against  a  long  spur  ("Cg."  on  map). 
Probablv  this  conglomerate  underlies  the  glacial  drift  all  about  here, 
as  it  does  in  the  northeast  part  of  Joliet  and  elsewhere. 

ALLUVIAL  FANS  AND  CONES. 

Since  the  outlet  of  Lake  Chicago  stopped  flowing  and  its 
valley  floor  is  all  but  abandoned,  the  excess  of  detritus  brought 
down  by  the  tributary  streams  has  in  many  places  built  up 
distinct  fans  and  conos.  One  of  these,  near  Joliet,  a  broad,  flatfish  fan 
of  sand,  may  be  seen  at  the  mouth  of  a  small  ravine  which  issued  from 
the  high  bluff,  half  a  mile  northeast  of  the  penitentiary.  Were  the  old 
outlet  restored,  it  would  collect  all  this  waste  and  carry  it  down  the 
valley;  but  without  a  full  sized  river  to  receive  and  transport  the  ma- 

1  "Illustrations  of  the  Huttonian  theory  of  the  earth,"  p.   102,   1802. 

2  The  post-glacial  interval  during  which  the  surface  of  the  "Wisconsin"  drift 
has  ben  exposed  to  stream  development  seems  to  be  somewhere  between  20.000  and 
60.000  vears  long.  (Chamberlin  and  Salisbury's  "Geology,"  Vol.  Ill,  p.  420.) 
This  portion  of  Illinois  was  uncovered  by  the  ice  sheet  soon  after  it  began  to  re- 
treat, for  the  terminal  moraine  of  the  last  great  ice  advance  lies  only  a  few  miles 
west  of  Joliet.  Hence  the  drift  surface  here  may  have  been  uncovered  50,000,  or 
at  least  nearly  20,000  years  ago. 


GOLDTHWAIT.]  HISTOEY    OF    THE    LOWER    DES  PLAINES.  65 

terial,  the  tributary,  when  swollen  by  floods,  is  forced  to  drop  its  load 
where  it  debouches  on  the  flat  valley  floor ;  and  in  so  doing  it  is  choked 
and  split  into  innumerable  distributaries,  after  the  fashion  of  fan- 
building  streams.  If  we  knew  just  how  much  sediment  was  being 
brought  down  by  this  little  tributary  each  year  (probably  almost  wholly 
during  severe  floods,  and  knew  the  total  volume  of  the  fan,  we  might 
obtain  from  it  a  rough  measure  of  the  number  of  years  since  the  outlet 
stopped  running — rough,  because  the  rate  of  growth  of  the  fan  has 
probably  varied  much  from  time  to  time. 

A  group  of  three  well  marked  cones  may  be  seen  along  the  base  of 
the  steep  80-foot  bluff  beside  the  trolley  road  half  a  mile  southwest  of 
Willow  Springs.  They  rise  with  moderately  steep  slopes  thirty  feet 
above  the  road,  where  each  has  its  apex  in  a  steep,  narrow  ravine.  The 
longest  of  the  cones  is  some  flfteen  rods  from  apex  to  base. 

These  cones  and  fans  exemplify  on  a  small  scale  the  alluvial  de- 
posits which  border  the  great  valley  of  California,  where,  with  a  rich 
soil  and  ideal  facilities  for  irrigation,  the  fans  have  been  transformed 
into  great  fruit  orchards. 


-5  G 


66  THE    DES  PLAINES    VALLEY.  [BULL.  NO.  11 


CHAPTER  VI. 


PHYSIOGRAPHIC  HISTORY  OF  THE  UPPER  DES  J'LAIXES 

RIVER. 

DEPOSITION   or   THE   TILL  RIDGES. 

In  the  preceding  chapter  it  has  been  explained  how  the  great  V- 
shapcd  belt  of  upland  which  encircles  the  south  end  of  Lake  Mich- 
igan— the  Valparaiso  moraine — was  built  up  under  the  edge  of  a  tongue 
of  ice  whicli  occupied  the  lake  basin.  So  long  as  the  melting  of  the 
ice,  at  the  liorder  of  this  tongue  or  lobe,  was  only  fast  enough  to  balance 
the  forward  movement  of  the  ice  mass,  the  ice  border  was  nearly 
stationary;  and  all  the  rock  debris,  or  "drift,"  that  was  carried  forward 
to  the  edge  of  the  glacier  was  banked  up  to  form  the  moraine.  At 
length  the  climate  moderated  somewhat,  and  "melting  came  to  exceed 
advance.  The  Lake  Michigan  ice  lobe  shrank  back  toward  the  center 
of  the  lake  basin — not  steadily,  however,  but  spasmodically.  Several 
times  the  ice  front  halted  in  its  retreat,  and  each  time  it  built  beneath 
its  edge  a  broad  ridge  of  till,  lower  and  smoother  than  the  Valparaiso 
moraine  but  like  it  in  origin.  Thus  there  grew  up  in  Cook  and  Lake 
counties  three  successive  till  ridges  of  the  "lake-border  morainic  sys- 
tem," between  the  Valparaiso  moraine  and  L^ke  Michigan.  Between 
them  were  lowlands  of  exceedingly  faint  relief. 

In  Racine  and  Kenosha  counties  (Wisconsin)  the  lake  border  ridges 
are  five  in  number,  but  passing  southward  into  Illinois  they  merge  to 
form  three  (See  Fig.  1.)  They  do  not  continue  around  the  south  end 
of  the  lake,  but  terminate  in  Cook  county,  as  shown  on  the  map;  the 
inner,  or  east  ridge,  at  Winnetka ;  the  outer,  or  west  ridge,  north  of 
Oak  park.  In  Indiana  and  Michigan,  however,  they  reappear  inside 
the  Valparaiso  moraine.  The  outermost  of  the  lowland  belts  between 
the  west  ridge  and  the  Valparaiso  moraine  forms  the  basin  of  the 
Des  Plaines  river,  above  Oak  Park.  There  the  ending  of  the  west 
ridge  allows  the  Des  Plaines  till  plain  to  open  upon  the  broad  Chicago 
plain. 

In  detail  of  relief,  these  border  ridges  are  very  weak.  Instead  of 
the  marked  knob-and-kettle  topography  of  typical  terminal  moraine, 
their  surfaces  present  low,  undulating  swells  and  sags,  faint  knolls  and 
shallow  sloughs.     Only  when  followed  for  a  long  distance  or  plotted  on 


GOLDTHWAIT.]  HISTORY   OF    THE    UPPER    DES  PLAINES.  67 

a  map  is  the  ridgelike  character  appreciated,  so  gentle  are  tlie  lateral 
slopes.  At  Park  Eidge,  for  instance,  the  outer  moraine  is  al^ont  two 
miles  broad,  and  its  crest  only  twentj'-tive  feet  higher  than  the  till-plain 
of  the  Des  Plaines  valley.  The  west  slopes  of  the  till  ridges  are  some- 
what more  pronounced  than  the  east  ones.  As  the  ice  border  receded 
and  these  till  ridges,  with  their  intervening  lowlands,  appeared,  a  new 
drainage  system  began  to  develop.  At  first,  doubtless,  the  streams  which 
flowed  through  the  depressions  were  burdened  by  outwash  from  the 
ice,  and  started  to  form  alluvial  plains  or  valley  trains,  like  those  of 
the  lower  Des  Plaines  valley,  described  in -Chapter  V,  and  Pigs.  8  and  9. 
The  depression  between  the  east  and  middle  belts  of  the  Valparaiso 
moraine,  now  followed  by  Salt  creek,  above  Pullersburg,  and  by  Flag 
creek  below,  was  doubtless  occupied  thus  early  by  streams.  Probably 
the  singular  bend  of  Salt  creek  at  Pullersburg  (See  Fig.  10)  was  gained 
at  this  time,  through  an  initial  depression  which  ran  transverse  to  the 
east  ridge  and  had  been  an  avenue  of  glacial  discharge  like  the  sag  in 
the  west  ridge  north  of  Joliet  (See  Fig.  8),  or  like  those  above  Lemont, 
though  less  marked. 

The  risfht-angled  turn  at  Pullersburg,  bv  which  Salt  creek  leaves 
the  inter-morainic  depression  close  to  the  head  of  Flag  creek  has  drawn 
the  attention  of  writers  on  the  geology  of  the  district,  at  various  times. 
The  relation  of,  the  two  streams  resembles  that  which  frequently  re- 
sults from  '^river  piracy,"  the  capture  of  the  upper  portion  of  a  stream 
by  the  headward  extension  of  a  more  rapidly  growing  and  more  deeply 
entrenched  neighboring  stream.  The  more  rapid  growth  of  the  "pirate" 
is  usually  attributed  to  advantage  from  a  shorter,  steeper  course,  or  of 
a  weaker  rock  structure  to  encounter,  or  of  a  larger  volume  (perhaps  ■ 
because  of  heavier  rainfall.)  In  the  present  case,  it  might  seem  that  the 
upper  part  of  an  ancestral  "Flat  creek,"  which  followed  the  lowland 
southward  past  Fullersburg,  was  captured  by  the  headward  growth 
of  a  transverse  stream  which  had  begun  its  growth  on  the  east  slope  of 
the  moraine,  (i.  e.,  the  present  lower  course  of  Salt  creek).  The  upper 
part  of  this  ancient  Flag  creek,  above  Fullersburg,  would  thus  become 
a  part  of  Salt  Creek,  and  would  be  diverted  into  the  Des  Plaines  at 
Riverside,  while  the  lower  part  of  it  would  be  left  in  a  beheaded  con- 
dition, the  Flag  creek  of  today.  Ko  positive  evidence,  however,  of  river 
capture  at  this  place  has  been  found ;  nor  does  there  seem  to  have  been 
,  any  reason  for  piracy.  Salt  creek,  below  Fullersburg,  seems  to  have 
had  no  advantage  over  Flag  creek,  either  as  to  the  length  of  its  course 
or  as  to  the  structure  it  encountered.  So  the  rather  singular  escape  of 
Salt  creek  from  the  broad  valley  seems  to  be  best  explained  merely 
as  one  of  the  freaks  of  glacier-made  drainage,  inspired  by  an  irregu- 
larity of  the  newly  exposed  surface  of  drift. 

LAKE   CHICAGO. 
GUENWOOD    STAGE. 

While  the  ice  sheet  was  withdrawing  from  the  Valparaiso  moraine 
to  its  next  position,  waters  gathering  along  its  border  in  the  Chicago 


<)8 


THE    DES  PLAINES   VALLEY, 


[BULL.    NO.   U 


district  began  to  assi;me  the  outline  of  a  crescentic  lake,  glacial  Lake 
Chicago  (Fig.  11.)  The  overflow  of  this  lake  escaped  across  the  Val- 
paraiso moraine  along  the  line  of  the  lower  Des  Plaines  valley. 


Fig.  16.  Part  of  Lake  Chicago  during  the  Glenwood  stage  (copied,  with  some 
modification,  from  Alden).  Outline  of  Des  Plaines  bay  inferred  from  the  50-foot 
contour  on  the  map  of  the  Sanitary  district.  Hachures  show  wave-cut  and  river- 
cut  bluffs ;   dots  show  beaches  and  spits. 

A  long  shallow  arm^  of  the  lake,  two  or  three  miles  wide,  reached 
northward  from  Oak  Park  up  the  depression  between  the  west  ridge  and 
the  Valparaiso  moraine  to  the  vicinity  of  Franklin  park  (Fig.  16). 
Further  north  the  inter-morainic  depression  was  probably  a  long  sloughy 


GOLDTHWAIT]  HISTOEY   OF   THE   UPPER    DES  PLAINES.  69 

on  which  the  upper  Des  Plaines,  fed  largely  by  the  melting  of  the  ice 
to  the  north,  and  subject  to  overloading  with  Avaste,  followed  an  ill- 
defined,  "braided"  course.  As  the  ice  border  melted  back,  leaving  this 
long  bay  or  slough,  outwash  gravels  accumulated  on  its  floor  to  a  depth 
of  several  feet.  These  deposits  of  stratified  gravel  are  from  10  to  13 
feet  thick  near  the  village  of  Des  Plaines.  A  thin  overlying  sheet  of 
brown  sand,  used  as  moulding  sand  at  the  iron  foundry,  may  record  the 
change  from  the  overloaded,  glacier-fed  stream  to  the  normal  stream  of 
diminished  volume  and  load,  which  followed  the  withdrawal  of  the  ice 
from  the  vicinity.  Although  the  shallowness  of  the  bay  prevented  the 
development  of  recognizable  shore  topography,  its  boundary  may  be 
considered  to  follow  the  contour  which  is  fifty  feet  above  Lake  Michigan, 
for  that  is  about  the  altitude  of  Lake  Chicago  at  its  earliest  stage,  judg- 
ing from  the  altitude  of  well  defined  beaches  in  the  Chicago  district. 

The  largest  stream  tributary  to  the  bay  at  this  highest,  or  "Glenwood" 
stage  was  doubtless  the  upper  Des  Plaines,  which  seems  to  have  entered 
it  not  far  above  Franklin  park.  The  smaller  creeks  which  head  west  of 
the  valley  on  the  Valparaiso  moraine  and  are  now  tributary  to  the 
main  river  between  Des  Plaines  village  and  Maywood  could  have  brought 
no  significant  amount  of  sediment  into  the  bay,  though  their  courses 
above  the  50-foot  level  were  no  doubt  already  established. 

The  Oak  Park  Spit. — ^Across  the  mouth  of  Des  Plaines  bay  a  long 
spit,  or  bar,  was  constructed  by  the  waves  and  shore  currents  of  the 
lake  as  they  swept  their  supply  of  beach  gravel  and  sand  southward 
in  the  direction  of  the  prevailing  drift  (See  Figure  17).  From  the  be- 
ginning of  the  spit,  where  it  extends  out  from  the  end  of  the  west  till 
ridge  north  of  Oak  Park,  to  its  termination  near  the  Twelfth  street 
bridge,  the  distance  is  about  three  and  a  half  miles.  As  far  south  as 
the  point  where  it  crosses  the  Chicago  and  North-Western  railway  at 
Oak  Park  its  form  and  height  make  it  appear  to  have  been  a  visible  reef, 
rising  above  the  lake  during  the  Glenwood  stage  and  separating  the 
lake  from  the  bay.  Its  southern  half,  however,  is  lower  and  flatter, 
and  probably  was  submerged.  Spits  and  bars  like  this  one  grow  up  only 
along  irregular  shores.  They  express  a  more  or  less  successful  attempt 
on  the  part  of  the  waves  and  currents  to  replace  the  re-entrants  of  a 
shoreline  with  straight  or  gently  curved  beaches.  In  order  to  see  how 
the.  Oak  Park  spit  was  constructed,  we  must  understand  the  conditions 
under  which  beach  material  moves   along  shore. 

Ordinarily  during  a  storm  the  waves  run  ashore  obliquely  rather 
than  straight  on;  for  it  does  not  often  happen  that  the  wind  is  blowing 
perpendicular  to  the  shore.  When  the  shore  line  is  irregular,  the 
chances  for  a  straight  on-shore  wind  at  any  place  are  still  smaller.  At 
most  places  the  wind  strikes  the  shore  at  an  angle,  and  the  waves  run 
up  more  or  less  obliquely.  So  there  comes  about  an  along-shore  trans- 
lation of  water  in  the  form  of  a  deflnite  current.  The  more  oblique 
the  wind  and  the  greater  its  force,  the  swifter  is  this  current.  Only 
during  storms  is  the  shore  current  sufficiently  strong  to  transport  sand 
and  gravel  as  it  is  danced  up  and  down  by  the  breakers. 


70 


THE    DES  PLAINES   VALLEY. 


[BULL.   NO.   11 


Fig.  17.  Map  of  the  district  about  Oak  Park  and  Maywood  (from  map  of  the 
Sanitary  district).  Contour  interval,  5  feet  above  Chicago  datum.  Oak  Park  spit 
indicated  by  dotted  pattern  ;  form  of  Des  Plaines  valley,  by  contours. 


GOLDTHWAIT]  HISTORY    OF   THE   UPPER    DES  PLAINES.  (1 

At  a  given  place  on  the  coast  the  shore  current  may  be  reversed  from 
time  to  time  as  the  storms  bring  waves  from  different  quarters.  As  a 
rale,  however,  the  Avind  from  one  direction  is  the  dominant  wind.  It 
may  almost  invariably  be  the  strongest,  or  it  may  last  longer  than  any 
other  storm  Avind,  or  it  may  have  a  greater  "fetch"  across  the  l-ike  or 
bay;  or  these  elements  may  be  combined.  In  any  case,  the  wind  from 
one  direction,  usually  sweeps  so  much  stronger  waves  that  it  controls 
the  movement  of  beach  material  along  shore.  On  the  southwest  shore 
of  Lake  Michigan  the  dominant  strong  wind  (i.  e.,  storm-wind)  comes 
from  the  north  and  northeast.  Sweeping  some  200  miles  lengthwise 
of  the  lake,  it  developes  stronger  waves  than  the  winds  from  other 
directions.  It  matters  little  that  southeast  storms  are  more  frequent 
than  "northeasters,"  and  the  southeast  winds  fully  as  strong  as  those 
from  the  northeast.  Our  shores  at  the  southwest  corner  of  the  lake 
are  relatively  sheltered  from  the  south  and  exposed  to  the  north ;  hence, 
the  dominant-  shore  current  along  the  Illinois  border  of  the  lake  runs 
from  north  to  south,  and  has  done  so  ever  since  glacial  Lake  Chicago 
first  took  shape. 

Waves  and  shore  currents  always  act  together.  On  shelving  shores, 
where  the  Avaves  in  time  of  storm  break  in  a  long  line  some  distance 
off-shore,  the  agitation  of  sand  and  gravel  beneath  the  breakers  offers 
a  chance  for  the  shore  currents  to  shift  the  particles  along  the  line 
inch  by  inch.  Eelatively  large  pebbles,  while  thus  raised  in  momentary 
suspension  beneath  a  breaking  wave,  may  be  Avorked  along  by  a  current 
which  Avould  be  too  Aveak  to  move  them  unaided.  The  abundance  of 
gravel  in  the  Oak  Park  spit,  Avith  pebbles  even  tAvo  inches  in  diameter, 
ceases  to  be  surprising  Avhen  it  is  remembered  that  the  drift  of  debris 
along  a  spit  is  accomplished  by  the  combined  forces  of  Avaves  and  currents. 

Supplementing  the  shore  currents,  the  advance  and  retreat  of  the 
waves  up  and  doAvn  the  beach  when  the  surf  is  running  in  obliquely 
causes  a  drift  of  beach  material  along  shore  at  the  water's  edge.  The 
wave  dashes  diagonally  up  the  beach,  sAveeping  sand  and  gravel  with 
it;  then  receding  the  water  pulls  back  some  of  the  waste,  either  straight 
doAvn  the  slope  or  still  somewhat  obliquely  along  the  beach.  Thus  a 
pebble  or  grain  of  sand  journeys  along  the  shore  in  a  zig-zag  path,  stop- 
ping from  time  to  time,  to  be  soon  picked  up  by  other  waves  and  carried 
farther  on.  When  an  off-shore  reef  of  sand  has  grown  up  to  Avater-level, 
it  will  be  built  up  farther  into  a  barrier  by  material  shifted  along  shore 
by  the  waves. 

So,  during  the  Glenwood  stage  of  Lake  Chicago,  the  strong  shore  cur- 
rent which  swept  southward  along  the  cliff  border  of  the  till  ridge  from 
Norwood  Park  past  Dunning  and  Montclair,  and  out  across  the  mouth  of 
Des  Plaines  bay  found  its  velocity  somcAvhat  checked  by  the  increasing 
depth  of  water  (its  energy  becoming  diffused)  and  Aveakening,  deposited 
its  load  of  sand  and  gravel  in  spit-like  form.  Once  started,  the  spit  gi-eAV 
southward  and  westward  by  continued  addition  to  its  free  end,  much 
as  a  railway  embanlvment  is  extended  by  a  train  of  cars  which  carry 
gravel  out  to  a  dumping  place  at  its  extremity.  Thus  the  accumulation 
not  only  rose  above  lake  level,  but  grew  in  length.    As  the  spit  reached 


72  THE   DES  PLAINES   VALLEY.  [bull.  no.  11 

out  into  the  bay  it  turned  somewhat  toward  the  west,  following  the  bend 
which  the  shore  current  made  in  its  delayed  attempt  to  enter  the  re- 
entrant. The  most  pronounced  part  of  the  curve  comes  at  Oak  Park 
avenue  and  Ontario  streets,  where  the  spit  bends  rather  sharply,  crossing 
the  grounds  of  Scoville  Institute,  and  takes  nearly  westerly  course  along 
Lake  street.  This  carving  of  the  spit  was  not  accomplished  by  a  simple 
continuous  growth  along  the  line  of  deflected  current.  Several  times 
the  growing  end  of  the  spit  was  temporarily  deflected  as  if  by  the  waves 
of  a  series  of  unusually  severe  storms,  which  turned  the  shore  current 
farther  into  the  bay.  Later,  the  normal  direction  of  the  shore  current 
was  restored,  however,  and  the  spit  grew  southward  as  before,  the  tem- 
porary hook  being  left  behind  the  new  outer  beach  ridge.  The  most  dis- 
tinct hook  of  this  sort  lies  just  north  of  Lake  street,  between  Kenil- 
worth  avenue  and  Marion  street.  Another,  nearly  obliterated  by  street 
grading,  may  be  traced  from  Euclid  and  Superior  avenues  westward  to 
Elizabeth  court;  and  a  fragment  of  a  third  appears  in  the  yards  on  the 
north  side  of  Lathrop  avenue  west  of  Harlem  avenue.  This  hooked  ex- 
tension of  the  Oak  Park  spit  seems  formerly  to  have  reached  nearly  a 
mile  west,  to  Eiver  Forest ;  but  the  extreme  f aintness  of  its  slope,  and  the 
destructive  grading  of  the  railway  and  the  streets  have  left  little  trace  of 
it.  The  50-foot  contour  on  the  carefully  prepared  map  of  the  Sanitary 
District  (Figure  17),  however,  as  well  as  the  360-foot  contour  of  the 
less  detailed  Eiverside  Sheet  of  the  U.  S.  Geological  Survey  (where  alti- 
tudes refer  to  sea  level)  indicate  its  trend. 

In  the  vacant  block  between  Linden  and  Euclid  avenues.  Oak  Park, 
and  north  of  Superior,  the  spit  has  the  form  of  a  very  pronounced  ridge, 
and,  like  most  of  the  old  beaches,  is  clothed  with  a  belt  of  oaks.  Its 
crest  rises  more  than  15  feet  above  the  former  lake  floor  to  the  south- 
east, and  nearly  10  feet  above  the  old  bay  floor  to  the  northwest.  The 
back  slope  is  somewhat  steeper  than  the  outer  or  lakeward  side.  The 
gravelly  condition  is  revealed  in  shallow  cuts  near  the  sidewalks.  This 
north  part  of  the  Oak  Park  spit,  with  its  characteristic  beach  profile, 
from  its  beginning  at  the  south  end  of  the  till  ridge  (north  of  Division 
street  and  Eidgeland  avenue)  to  the  railroad  station,  probably  rose  above 
the  water,  separating  .the  bay  from  the  lake. 

South  of  the  railroad  the  spit  finds  extension  in  a  lower  and  much 
flatter  ridge  of  gravels,  which  is  followed  by  Des  Plaines  avenue  for 
over  a  mile,  or  nearly  to  Twelfth  street.  This  portion  of  the  spit  rises 
less  than  10  feet  al)ove  the  lake  floor,  with  faint  slopes,  and  so  seems  very 
probable  to  have  been  a  subaqueous  reef  along  which  beach  material  was 
drifting,  but  which  never  rose  as  high  as  lake  level.  It  is  composed  very 
largely  of  fine  gravel  with  pebbles  less  than  1  inch  in  diameter,  as  can 
be  seen  in  the  cuts  beside  the  Great  Western  railway:  but  near  the  south 
end  of  the  spit,  in  Waldheim  cemetery,  artificial  pits  near  Twelfth  street 
show  an  ab-mdance  of  coarse  gravel  in  which  the  pebbles  are  2  inches  in 
diameter.  The  strata  here  dip  steeply  toward  the  south,  the  direction 
in  which  the  end  of  the  spit  was  being  extended. 

The  reason  for  the  southerly  direction  of  this  half  of  the  Oak  Park 
spit  is  somewhat  in  doubt.     It  has  been  explained  as  "probably  due  to 


GOLDTHWAIT.]  HISTORY   OF    THE    UPPER    DES  PLAINES.  78 

the  combined  action  of  the  northeast  winds  and  the  current  of  outward 
flow  from  the  estuary.  The  wind  turned  the  spit  westward  until  the 
outlet  of  the  estuary  was  somewhat  constricted,  when  the  outward  flow  of 
water  became  sufficiently  strong  to  deflect  the  spit-building  current 
again  southward."^  In  a  bay  of  such  length  and  width,  with  a  tributary 
stream,  the  Des  Plaines,  to  maintain  an  outward  flow  of  water,  this  ex- 
planation may  fairly  be  questioned.  It  seems  much  more  probable  that 
wave  action  in  the  bay  with  wind  from  the  north,  producing  a  current  on 
the  bay  side  of  the  spit,  would  be  competent  to  prevent  its  extension  in 
a  westerly  direction,  and,  in  conjunction  with  the  dominant  southwest- 
ward  drift  in  the  lake,  would  direct  the  spit  southward. 

While  the  Oak  Park  spit  did  not  wholly  shut  in  the  Des  Plaines  bay, 
its  construction  went  far  toward  replacing  the  initial  irregular  shoreline 
with  a  gentle  curve,  such  as  characterized  the  more  advanced  stages  of 
shore  development. 

Shoreline  between  Maywood  and  Mt.  Forest. — That  part  of  the  Glen- 
wood  shoreline  which  lies  west  of  the  Des  Plaines  river  is  neither  so 
characteristic  nor  so  interesting  as  the  portion  near  Oak  Park.  Across 
the  mouth  of  the  Des  Plaines  bay  west  of  the  end  of  the  Oak  Park  spit, 
a  hardly  perceptible  beach  was  built  at  the  border  of  the  shallow  water 
south  of  Maywood.  A  small  tract  of  land  here,  around  Broadview,  was 
probably  a.  swampy  island  close  to  lake  level.  North  of  LaGrange,  how- 
ever, the  gentle  east  slope  of  the  Valparaiso  moraine  is  bordered  by  a 
rather  sloping  bank  15  to  20  feet  high,  which  faces  the  lake  floor.  This 
seems  to  have  been  a  low  lake  cliff  rising  from  the  water's  edge  like  the 
bluffs  along  the  present  lake  shore  north  of  Evanston.  The  height  of  the 
lake  floor  at  the  base  of  the  cliff  is  approximately  50  feet  above  Lake 
Michigan,  the  altitude  of  the  extinct  lake  so  far  as  can  be  judged  from 
the  best  developed  terraces  and  beaches.  This  cut  bluff  may  'be  traced 
northward  from  La  Grange  more  than  two  miles  to  Salt  creek,  where  it 
fades  away.  Just  east  of  the  Butterfield  road  the  crest  of  the  bluff  is 
■crowned  with  a  ridge  of  gravels  for  a  distance  of  over  a  quarter  of  a 
mile.  It  is  plainly  seen  in  the  cemetery  and  in  the  gravel  pits  a  few 
rods  north.  Since  the  crest  of  the  ridge  stands  10  feet  or  more  above 
the  base  of  the  bluff,  it  seems  necessary  to  regard  it  as  the  beach  of  a 
somewhat  earlier  period,  probably  the  very  beginning  of  the  Glenwood 
stage,  when  the  lake  stood  for  a  while  as  high  perhaps  as  60  feet  above 
Lake  Michigan.  This  beach  ridge  controls  the  course  of  Salt  creek  for  a 
considerable  distance,  as  far  north  as  Twenty-second  street,  where  the 
creek  turns  and  enters  upon  the  lake  floor.  This  northward  deflection 
indicates  that  the  direction  of  shore  currents  near  La  Grange,  in  the 
Glenwood  stage,  was  towards  the  north.  That  is  to  be  expected,  because 
La  Grange  stands  near  the  mouth  of  the  old  bay,  where  exposure  to 
east  and  southeast  winds  was  great,  while  exposure  to  the  north  was 
much  reduced  by  the  protection  of  the  Oak  Park  spit. 

South  of  La  Grange,  as  far  as  McCook,  the  same  cut  bluff  may  be  fol- 
lowed; but  it  is  not  always  plainly   defined,   for  cultivation  of  fields 


lAlden,  U.   S.  Geol.   Surv.,  Chicago  Folio  No.   81,  p.  8.      1907. 


74  THE    DES  PLATNES   VALLEY.  [bull.  NO.  11 

seems  to  have  greatly  softened  its  outlines.  Eounding  the  rocky  hillside 
at  MeCook.  it  loses  distinctness  and  passes  along  the  uneven  border  of 
the  moraine  to  the  head  of  the  outlet  near  'Sit.  Forest. 

Around  the  northeast  end  of  ^It.  Forest  island,  imperfect  traces  of  a 
Glenwood  bluff  may  be  seen  here  and  there.  Xear  Archer  road  the  ter- 
race at  the  base  of  the  bluff  is  somewhat  inclined,  and  stands  a  little 
lower  than  the  Glenwood  level.  Further  east,  near  Hartman  avenue  and 
Eigthty-seventh  street,  two  distinct  beach  ridges  mark  the  Glenwood 
shoreline. 

CALCMET  STAGE. 

Emergence  of  the  foor  of  Des  Plaines  hay. — As  the  outlet  of  Lake 
L  nicago  was  deepened  by  erosion,  the  level  of  the  lake  fell  rather  gradually 
from  50  feet  to  about  35  feet  above  Lake  Michigan,  where  for  a  time 
it  remained  nearly  constant.  The  conditions  which  seem  to  have  deter- 
mined this  halt  at  the  35-foot  level  have  already  been  set  forth.  As  the 
lake  fell,  large  areas  formerly  under  shallow  water  became  land.  The 
floor  of  Des  Plaines  bay  emerged  to  form  a  broad  marshy  plain,  whicli 
stretched  soith  to  the  new  '^'Calumelr''  shore  at  Eiverside.  (See  Figurri 
18.)  Down  the  ill-defined  slope  of  the  bay  plain,  the  Des  Plaines  river 
extended  its  course,  with  many  crooks  and  bends,  while  the  few  creeks 
which  headed  on  the  Valparaiso  moraine  and  were  formerly  tributary  to 
the  bav  were  now  Joined  or  ''engrafted"  to  the  trunk  stream.  Salt 
creek  found  a  devious  path  eastward  and  southward  on  the  new  plain, 
almost  failing  to  reach  the  Des  Plaines,  but  connecting  with  it  at  the 
lake  shore  behind  a  beach  at  Eiverside. 

This  engrafting  of  independent  streams  to  form  a  single  system  on 
the  emerging  of  the  Des  Plaines  plain,  is  comparable  in  a  general  way 
to  the  growth  af  the  lower  Mississippi  SAstem.  During  early  Tertiary 
time  a  long  arm  of  the  Gulf  of  Mexico  reached  up  the  Mississippi  valley 
as  far  as  Cairo.  Tribitar}-  to  the  bay  were  several  large  rivers;  the 
upper  Mississippi  and  the  Ohio  at  its  head,  the  Tennessee  on  its  east  side, 
and  the  White,  Arkansas,  and  Eed  rivers  on  the  west  side.  Xear  the 
close  of  the  Tertian'  period  warpings  of  the  earth's  crust  were  accom- 
panied by  a  withdrawal  of  the  sea  from  the  land.  The  valley  of  the 
lower  Mississippi  emerged,  and  the  several  rivers  united  on  the  plain  to 
form  the  single  great  river  system,  whose  drainage  area  is  a  million  and 
a  quarter  square  miles.  The  Amazon  system  of  Brazil,  with  twice  as 
great  a  drainage  basin,  has  been  made  in  a  similar  way. 

The  crooked  path  of  the  Des  Plaines  river,  which  was  determined  thus 
early  by  original  inequalities  of  slope  on  the  newly  exposed  bay  floor,  ac- 
counts in  large  measure  for  its  present  course  and  the  width  of  the  valley 
which  it  has  excavated.  While  the  lake  stood  at  the  Calumet  level,  the 
river  began  its  work  of  excavating  a  channel  along  its  course,  gradually 
entrenching  itself  below  the  bay  plain.  Later,  as  the  lake  waters  fell  and 
the  base  level  of  erosion  for  the  river  was  lowered,  the  entrenchment  of 
the  river  progressed  to  greater  depth.  The  consideration  of  this  matter 
is  left  for  a  later  section. 


GOLDTHWAIT.] 


HISTOBY   OF    THE   UPPEE    DES  PLAINES. 


to 


The  Calumet  shoreJine. — Tlie  margin  of  the  lake  at  this  stage  crossed 
the  plain  of  the  Des  Plaines  hay  ohliquely  from  Austin  to  Biverside. 
This  portion  of  the  lake  shore  is  marked  in  some  places  hv  a  beach  slope 
Oi  moderate  definition.  South  of  Twelfth  street  ( where  it  crosses  Austin 
avenae  near  the  ^McKinley  school)  the  ridge-like  form  of  the  beach  be- 
comes more  and  more  marker!. 


Fig.    18.     Part    of   Lake    Chicago    during   the    Calumet    stage.      (Modified    from 
Alden.) 

An  interesting  geographic  response  to  the  shore  topography  of  this 
old  lake  stage  is  seen  in  the  many  old  farm  houses  and  barns  along  the 
crest  of  the  ridge.     The  early  settlers  on  this  poorly  drained  Chicago 


76  THE   DES  PLAINES   VALLEY.  [bull.  no.  11 

plain  located  their  homesteads  on  the  dry,  sandy  beach  ridges,  A  char- 
acteristic old-time  farm  house,  now  almost  in  ruins,  stands  at  the  corner 
of  Austin  avenue  and  Twelfth  street.  Numberless  examples  of  this  sort 
might  be  given. 

At  Charles  Becker's  picnic  grove  (Twenty-second  street),  where  the 
La  Grange  trolley  car  crosses  the  beach,  the  characteristic  profile — a 
long,  gentle  front  slope  and  a  short,  moderately  steep  back  slope,  is 
plainly  seen.  Here,  as  is  frequently  the  case,  the  ridge  is  lined  with  old 
oak  trees,  and  was  formerly  followed  by  a  highway.  From  this  point 
south  for  a  mile  or  more  a  road  follows  the  beach  (See  Fig.  19).  Near 
the  Illinois  Central  railway  the  ridge  is  double.  A  second  crest,  on  the 
west  side  of  the  road,  stands  a  few  feet  lower  than  the  main  beach.  It 
suggests,  of  course,  that  the  plain  northwest  of  the  beach  was  formerly 
a  shallow  bay,  and  that  the  inner  crest  of  the  ridge  is  a  low  beach  built 
by  waves  from  the  bay  side  of  the  bar;  but  as  this  plain  seems  to  be 
somewhat  above  the  35-foot  level  it  seems  unlikely  that  it  was  submerged 
during  the  Calumet  stage. 

Through  the  east  part  of  Riverside  the  beach,  if  ever  strongly  de- 
veloped, has  been  effaced  by  artificial  grading.  It  reappears  distinctly 
west  of  the  Chicago,  Burlington  &  Quincy  railway  station,  running 
southwest  as  shown  in  Figure  19.  Close  behind  it,  the  Des  Plaines  river 
follows  a  deflected  course  from  the  railway  bridge  to  the  mouth  of  Salt 
creek.  There,  turning  abruptly  eastward  around  the  end  of  the  ridge 
and  again  sharply  northward,  it  runs  back  to  Riverside.  The  deflected 
path  of  the  river  above  Salt  creek  is  doubtless  due  to  the  southwestward 
drift  of  waste  along  the  beach.  Probably  the  Calumet  beach  ridge 
stretched  along  the  lakeward  border  of  a  marsh  near  the  mouth  of  the 
Des  Plaines  river  and  Salt  creek.  The  southwestward  movement  of 
material  on  the  beach  prevented  the  river  from  running  directly  out  to 
the  lake,  and  pushed  it  farther  and  farther  toward  the  southwest.  The 
return  couse  of  the  river  on  the  lakeward  side  of  the  beach  ridge  is,  of 
course,  of  later  origin,  and  will  presently  be  discussed.  At  one  place 
not  far  south  of  the  railway  bridge  the  river  cuts  obliquely  across  a 
branch  crest  or  spur  of  the  beach  ridge.  Beyond  that  point,  however,  to 
the  mouth  of  Salt  creek,  its  course  is  parallel  to  the  old  beach.  One 
should  realize,  of  course,  that  during  later  stages  the  river  has  deepened 
its  course  some  15  feet  below  the  bay  plain  and  the  swamp  of  the  Calu- 
met times.  The  beach  ridge  which  deflected  the  river  was  not  the  high, 
conspicuous  ridge  of  to-day,  but  the  relatively  low  beach  which  now 
forms  its  crest. 

Across  the  river,  between  Lyons  and  McCook,  there  is  no  clear  indica- 
tion of  the  shore  of  the  extinct  lake.  The  position  of  the  Calumet  shore 
may  be  inferred  from  the  35-foot  contour  of  the  Sanitary  District's  map 
(Figure  19),  which  indicates  that  it  bent  eastward  from  Lyons  in  a  long 
curve,  passing  around  the  gently  sloping  rock  elevation  east  of  Joliet 
avenue  and  returning  west  and  southwest  to  the  base  of  the  long  hill 
west  of  McCook.  There  it  lies  just  down  the  slope  from  the  Glenwood 
shoreline. 


STATE  GEOLOGICAL.  SURVEY. 


BULL.   NO.    11,   PL.    8. 


■AvU  . 

r 
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I  >JII  y 

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.'■*-"*  . 


A.     Young  Gulley  near  Reed's  Woods. 


B.     Calumet   Beach   Ridge   at   Summit. 


GOLDTHWAIT.]  HISTORY   OF    THE   UPPER    DES  PLAINES. 


77 


On  the  south  side  of  Lake  Chicago  the  shore  of  the  Calumet  stage 
runs  northwest  from  Blue  island  several  miles  to  Summit,  at  the  head 
of  the  outlet.  As  one  approaches  Summit  along  Archer  road  (the  route 
of  the  trolley  cars  from  Chicago  city  limits  to  Joliet,  shown  on  the 


Fig  19.  Map  of  the  district  about  Riverside  and  Summit  (from  map  of  the 
Sanitary  district).  Contour  interval,  5  feet  above  Chicago  datum.  Beach  ridges 
indicated  by   dotted   pattern. 


78  THE   DES  PLAINES   VALLEY.  [BULL.  NO.  11 

map^  Figure  19)  the  beach  ridge  is  seen  not  far  to  the  south,  rising  wilh 
pronounced  slope  15  or  20  feet  above  the  lake  plain.  Its  crest  is  higher 
than  the  40-foot  contour.  About  a  mile  east  of  Summit,  where  the  road 
ascends  the  ridge,  it  is  double-crested ;  the  south,  or  inner  crest,  standing 
a  few  feet  lower  than  the  outer  one.  From  here  westward  the  ridge 
widens  considerably,  showing  three  distinct  crest  lines,  and  at  Summit 
it  hooks  sharply  around  to  the  south,  forming  the  gateway  to  the  outlet 
of  Lake  Chicago.  There  seem  to  have  been  been  three  closely  set  hooks 
here  at  Summit,  one  overlapping  the  other ;  but  the  subsequent  widening 
of  the  outlet  during  the  Tolestou  stage  of  the  lake  cut  away  the  bends  of 
the  hooks,  leaving  only  their  main  stem  to  the  east  and  their  points  to 
the  south.  The  innermost  extends  from  the  turn  of  Archer  road  south- 
ward beyond  the  school  hoise,  with  characteristic  beach  profile.  The 
middle  ridge,  much  less  distinct,  crosses  Archer  road  just  opposite  the 
school  house  and  soon  dies  out.  Two  hundred  yards  farther  south,  the 
truncated  edge  of  the  outermost  ridge  appears  on  the  channel  bank  of 
the  outlet,  at  the  west  side  of  Archer  road.  Crossing  diagonally,  it  runs 
southward  several  hundred  yards,  and  flattens  out  near  the  railway 
crossing. 

Judging  from  the  height  of  the  ridge,  its  hooked  form  and  the  con- 
tours of  the  Sanitary  District's  map,  this  was  a  bar  during  the  Calumet 
stage,  shutting  off  a  broad  lagoon  and  marsh  that  stretched  southward 
as  far  as  Mt.  Forest  island.  There  was  probably  a  depth  of  10  feet  of 
water  for  a  mile  or  so  behind  the  bar,  and  extending  southwest  past  the 
Chicago  Union  Transfer  yards,  affording  some  wave  action  on  the  bay 
side  of  the  ridge.  Xot  far  southwest  of  this,  the  plain  rises  almost  im- 
perceptibly to  a  height  slightly  above  the  level  of  the  Calumet  stage,  so 
that  this  district  immediately  north  of  Mt.  Forest  island  was  undoubt- 
edly a  great  marsh. 

On  the  east  side  of  Archer  road,  near  Mt.  Forest  island,  may  be  seen 
a  low  beach  ridge  which  stretches  from  Bethania  cemetery  northeast- 
ward, across  the  fields.  It  is  marked  by  a  line  of  great  gnarled  oak  trees 
and  an  old  brick  farm  house.  This  beach  during  the  Calumet  stage  ran 
along  the  southwest  corner  of  the  marsh,  marking  off'  the  long  narrow 
arm  of  the  lake  which  led  to  the  outlet.  The  gateway  between  Summit 
and  McCook  might  in  one  sense  be  taken  as  the  head  of  the  outlet,  though 
the  actual  river  began  more  properly  at  Mt.  Forest,  at  the  head  of  the 
notch  in  the  Valparaiso  moraine. 

TOLESTON    STAGE. 

Extension  of  the  Des  Plaines  river  near  Riverside. — As  the  Chicago 
outlet  once  more  cut  down  its  fioor,  the  waters  of  Lake  Chicago  agaiii 
dropped  15  feet,  to  a  level  of  20  feet  above  Lake  ]\Iichigan.  The  shore- 
line withdrew  somewhat  towards  the  present  shore,  and  the  mouth  of 
the  Des  Plaines  river  was  extended  from  behind  the  end  of  the  Eiversido 
bar  to  a  point  near  the  spill-way  above  the  Santa  Fe  railway  bridge 
(Fig.  19).  In  this  extension  the  Des  Plaines  was  led  far  out  of  its  way 
by  the  irregularities  of  the  shallow  lake  floor.     From  the  end  of  the 


GOLDTHWAIT  ]  HISTORY   OF    THE   UPPER    DES  PLAINES.  79 

Riverside  beach  ridges,  where  a  broad  belt  of  slightly  higher  ground  bor- 
dered the  lake  on  the  south,  the  river  turned  sharply  northwest  along 
the  outer  side  of  the  beach  to  Riverside,  where  it  again  turned  east  and 
south  down  the  slope  to  the  plain  to  its  new  mouth  above  the  Ogden  dam. 
The  board  elevation  at  Lyons  which  prevented  the  extension  of  the 
river  straight  towards  Summit,  causing  the  return  course  to  Riverside, 
is  a  rocky  elevation  only  thinly  covered  with  till.  The  limestone  quarries 
of  Fred  Schultz  are  located  here,  near  the  bend  of  the  Des  Plaines.  As 
no  bed  rock  is  exposed  in  the  river  bank,  however,  it  is  altogether  prob- 
able that  the  recurving  of  the  river  to  Riverside  was  brought  about  not 
by  the  resistance  of  rock  encountered  in  the  river  bed,  but  rather  by  the 
initial  slope  of  the  old  lake  floor  around  the  elevation.  Thus  the  earlier 
deflection  of  the  river  behind  the  Calum'et  beach  was  supplemented  at 
the  beginning  of  the  Toleston  stage  by  an  opposite  deflection  on  the  .lake 
plain  along  the  outer  side  of  the  beach,  producing  the  peculiar  hairpin- 
like curve  which  is  shown  on  the  map  (Figure  19).  Salt  creek,  formerly 
entering  the  lake  behind  the  Riverside  beach  in  a  swamp  close  to  the 
mouth  of  the  Des  Plaines  river,  now  became  a  real  tributary  of  it.  The 
volume  thus  added  to  the  Des  Plains  system  was  very  considerable.  Salt 
creek  drains  an  area  of  110  square  miles,  or  one-fifth  as  large  a  basin  as 
the  main  river  above  Lyons.  It  gathers  its  volume  from  a  long  belt  of 
low  ground  within  the  Valparaiso  moraine.  The  current  of  Salt  creek 
where  it  enters  the  Des  Plaines  at  the  beginning  of  the  sharp  bend 
strongly  influences  the  direction  of  current  of  the  trunk  stream  at  that  '* 
point,  holding  it  oS.  from  the  outer  bank,  which  it  would  otherwise  be 
actively  trimming,  and  thus  tending  to  maintain  the  bend  in  a  fixed 
position. 

Reneived  trenching  of  the  valley. — The  lowering  of  the  lake  to  the 
Toleston  stage  was  equivalent  to  a  lowering  of  base-level  for  the  Des 
Plaines  river  about  15  feet.  So,  with  steepened  slope,  the  river  was  in- 
spired to  sink  its  channel  below  the  grade  already  established  during  the 
Calumet  stage,  and  deepened  its  trench  to  a  level  not  far  above  that  of 
the  present  valley  floor.  A  more  detailed  account  of  the  trenching  and 
the  associated  shifting  of  the  crooks  and  bends  in  the  river  will  presently 
be  given. 

The  Toleston  shoreline.-^The  shoreline  of  the  Toleston  stage  is 
marked,  between  HaAvthorne  and  the  river,  by  a  low  but  distinct  beach 
ridge  which  rises  seldom  more  than  10  feet  above  the  low  lake  plain. 
On  the  west  side  of  the  river  a  distinct  blufl^  not  over  10  feet  high  ap- 
pears along  the  base  of  the  gently  sloping  hillside  south  of  Lyons.  Fad- 
ing away  as  it  nears  Joliet  avenue,  the  shoreline  is  almost  lost  on  the 
old  lake  floor  near  McCook,  and  does  not  again  appear  at  all  plainly  on 
the  west  side  of  the  old  outlet. 

A  short  distance  east  of  Summit  the  outer  slope  of  the  great  Calumet 
beach  ridge  was  cut  away  by  the  lake  to  form  a  low  cliff,  in  the  Tolesto?i 
stage.  Just  northeast  of  the  village  of  Summit  this  is  replaced  by  a 
broad,  flatfish  beach  ridge  of  gravelly  constitution,  which  stands  only 
a  few  rods  north  of  the  higher  Calumet  ridge,  where  the  latter  is  ex- 
tensively opened  at  a  gravel  pit  (See  Fig,  19).     Here  is  a  -narticularly 


80 


THE  DES  PLAINES  VALLEY. 


[BULL.    NO.   11 


good  place  to  see  the  beaches  of  the  35-foot  and  20-foot  stages  close  to- 
gether, and  to  study  the  contrasted  features  of  beach  ridge  and  shore 
cliff.  The  stratification  of  the  beach  gravels  of  the  Calumet  ridge  is 
especially  v/ell  shown  in  the  gravel  pit. 


p-iG.    20.     Part   of    Lake    Chicago    during   the    Toleston    stage.      (Modified    from 
Alden.) 

From  Summit  southward  the  east  side  of  the  outlet  is  marked  for 
several  miles  by  a  steep  straight  bluff,  which  lies  j  ist  west  of  Archer 
road  and  is  plainly  seen  from  the  car  window  most  of  the  way  to  Willow 
Springs.     The  bluff  is  about  15  feet  high,  rising  from  the  20-foot  con- 


GOLDTHWAIT]  HISTORY   OF    THE   UPPEE    DES  PLAINES.  81 

tour  to  the  level  of  the  Calumet  lake  floor.  It  was  cut  by  the  outflowing 
river,  probably  at  the  time  when  the  removal  of  the  sill  of  bed  rock  at 
Lockport  caused  the  river  to  saw  down  its  bed  along  its  entire  course 
above  Lockport. 

SUBSEQUENT   CHANGES  LEADING  TO   FORMATION  OF  lAKE  MICHIGAN. 

The  manner  in  which  the  lake  fell  from  the  Toleston  or  20-foot  level 
to  a  level  below  the  present  Lake  Michigan,  and  then  rose  to  a  level  about 
12  feet  above  it  has  already  been  told.  It  was  while  the  lake  stood  at 
the  12-foot  level  that  the  broad  reef  of  sand  was  constructed  between 
Lincoln  park  and  South  Englewood,  shutting  off  the  Chicago  outlet. 
Because  of  this,  the  district  east  of  Summit,  including  the  greater  part 
of  the  city  of  Chicago,  was  probably  a  great  shallow  marsh,  with  only 
slight  and  sluggish  drainage  westward  through  the  abandoned  outlet. 

The  series  of  changes  which  led  to  the  disappearance  of  Lake  Algon- 
quin, to  the  complex  history  of  the  Nipissing  great  lakes,  and  finally  to 
the  present  chain  of  lakes  with  the  single  outlet  through  the  St.  Clair 
river,  has  been  given  in  the  preceding  chapter,  just  referred  to.  So  far 
as  the  history  of  the  Des  Plaines  river  is  concerned,  we  may  ignore  the 
details  of  these  changes  and  consider  simply  how  the  lowering  of  the 
lake  from  the  12-foot  level  to  the  present  one  affected  the  river.  As  thfe 
lake  fell,  the  slope  of  its  floor,  now  newly  exposed  near  Summit,  was 
hardly  sufficient  to  direct  the  Des  Plaines  river  southwestward  into  the 
head  of  the  old  outlet.  At  the  bend  which  the  river  now  makes  there, 
near  Ogden  dam  (See  Fig.  19),  a  well  defined  slough,  formerly  known 
as  Mud  lake,  leads  eastward  to  the  south  branch  of  the  Chicago  river. 
It  marks  a  line  of  escape  which  has  been  used  time  and  time  again  by 
the  Pes  Plaines  during  floods.  Here  was  the  old  Indian  portage,  where 
Marquette  and  other  early  explorers,  at  the  time  of  a  spring  freshet, 
could  paddle  their  canoes  from  Lake  Michigan  to  the  headwaters  of  the 
Illinois.  It  is  not  at  all  improbable  that  at  one  time  the  Des  Plaines 
river  discharged  wholly  through  this  slough,  into  Lake  Michigan.  If  so, 
its  southwestward  course  (which  we  have  called  the  "lower  Des  Plaines)^' 
is  a  very  recent  one.  The  natural  divide,  east  of  Mud  lake,  on  the  smooth 
plain  near  Kedzie  avenue,  may  have  been  built,  as  Mr.  Lyman  E.  Cooley 
suggests,  by  silts  from  the  river,  collected  behind  a  beaver  dam. 

EXCAVATION  OF  THE  VALLEY. 

It  has  already  been  explained  how  the  emergence  of  the  smooth  floor 
of  Des  Plaines  bay  when  the  lake  fell  from  the  50-foot  to  the  35-foot 
level  was  accompanied  by  the  extension  of  the  river  from  near  Franklin 
Park  southward  to  Eiverside.  Many  crooks  and  bends  were  caused  by 
faint  irregularities  of  slope  of  the  newly  exposed  surface.  The  slope  of 
the  bay  plain  from  the  50-foot  contour  near  Franklin  Park  down  to  the 
35-foot  level  at  Eiverside  is  exceedingly  gentle,  a  fall  of  15  feet  in  12 
miles.  This  is  somewhat  steeper,  however,  than-  the  present  slope  of  the 
Des  Plaines  river,  which  falls  only  5  or  6  feet  in  the  same  distance. 

.     —6  G 


82  THE   DES  FLAINES   VALLEY.  [bull.  no.  11 

During  the  Calumet  stage,  then,  with  an  initial  slope  of  about  II/2  feet 
per  mile,  the  river  may  have  reduced  its  slope  to  as  low  a  grade  as  it 
now  possesses — half  a  foot  to  the  mile,  by  sinking  its  channel  a  few  feet 
below  the  bay  plain.  The  river,  then,  during  the  Calumet  stage,  might 
have  deepened  its  trench  several  feet  below  the  level  of  its  broad  valley 
floor.'  The  subsequent  drop  from  Calumet  to  Toleston  level,  while  it  ex- 
tended the  mouth  of  the  river  only  a  short  distance,  reduced  its  base-level 
15  feet,  i.  e.,  made  it  possible  for  the  river  to  cut  15  feet  lower,  by  steepen- 
ing its  slope  and  increasing  its  velocity  and  its  efficiency  for  deepening 
its  bed.  Again,  when  the  lake  waters  fell  from  the  20-foot  mark  to 
essentially  the  present  level,  laying  bare  the  plain  between  Eiverside  and 
Summit  and  allowing  the  Des  Plaines  to  turn  southwest  down  the  floor 
-  ^  the  abandoned  outlet  channel,  the  local  base-level  was  lowered ;  erosion 
was  revived,  and  this  revival  was  transmitted  upstream,  causing  a  deep- 
ening of  the  channel.  In  the  subsequent  interval,  the  river  has  cut  its 
valley  about  10  feet  below  the  Toleston  level,  near  where  its  mouth  lay 
during  the  Toleston  stage.  Farther  up,  however,  the  deepening  has  been 
much  less,  because  it  has  cut  down  to  bed  rock,  revealing  the  surface  of 
the  ledges  at  three  places — .(1)  a  few  rods  below  the  Ogden  avenue 
bridge,  (2)  just  below  the  Riverside  dam,  and  (3)  on  Salt  creek  just 
above  its  junction  with  the  Des  Plaines.  Since  the  sill  of  limestone  at 
Eiverside  stands  almost  as  high  as  Toleston  level,  it  seems  to  have  pre- 
vented the  full  amount  of  deepening  above  Eiverside  after  the  Toleston 
stage. 

If  such  is  the  case,  there  have  been  three  steps  in  the  excavation  of  the 
trench-like  valley  above  Eiverside.  (1)  During  the  Calumet  stage  of 
Lake  Chicago  a  shallow,  winding  trench  was  cut  below  the  bay  plain, 
with  low  grade  appropriate  to  Calumet  base-level.  (2)  With  the  drop  of 
the  Toleston  stage,  a  second  period  of  deepening  began,  which  probably 
reduced  the  floor  of  the  trench  to  Toleston  base-level.  (3)  Since  the  low-? 
ering  of  the  lake  from  the  Toleston  to  the  present  level  there  has  been  a 
further  deepening  of  the  channel,  amounting  probably  to  only  a  few 
feet;  for  the  process  has  ben  effectively  checked  by  the  ledges  at  Eiver- 
side. 

Bearing  in  mind  these  points  of  erosional  history  of  the  upper  valley, 
.we  may  now  seek  to  explain  the  peculiar  details  of  the  valley  that  has 
been  excavated.  It  should  be  remarked  in  the  first  place  that  the  contour 
map  of  this  dir^trict  published  by  the  IT.  S.  Geological  Survey  (Eiver- 
side quadrangle),  with  its  rather  small  scale  of  one  mile  to  the  inch, 
lacks  details ;  so  the  expression  of  the  trench-like  valley  on  this  map  is 
quite  misleading.  It  is  shown  as  a  narrow,  wimling  trench  which  follows 
closely  every  crook  and  turn  of  the  river.  On  the  larger  and  more  de- 
tailed contour  map  drawn  by  the  Sanitary  District  (and  copied  in  part 
in  Fig  ires  17  and  19)  the  true  form  of  the  valley  comes  out  distinctly. 
It  is  a  trench  of  considerable  width,  not  infrequently  ten  times  as  broad 
as  the  channel  which  swings  across  its  floor  from  side  to  side  in  imper- 
fect meandering  fashion.  Compared  with  the  crooked  river  channel  the 
trench  of  the  valley  is  relatively  straight,  its  two  banks  constricting  tho 


GOLDTHWAIT]  HISTORY   OF    THE    UPPER    DES  PLAINES.  8B 

turns  and  sharply  definino;  its  meander  belt.  Where  the  river  impinges 
against  one  of  its  bluffs  there  is  a  steep  bare-faced  expos  ire  of  glacial 
drift  and  frequently  toppling  trees,  which  testify  to  the  lateral  sawing 
of  the  river  and  the  constant  widening  of  its  trench. 

Perhaps  the  most  instructive  view  of  this  lateral  cutting  is  to  be  had 
at  the  Madison  street  bridge,  near  Harlem.  (See  Fig.  17.)  On  the  north 
side  of  the  bridge  the  river  is  rapidly  trimming  back  its  left  bank,  ex- 
posing the  compact  glacial  drift  in  a  steep  15-foot  bluff.  As  fast  as  the 
river  saws  at  the  base  of  the  bank,  the  bowlder  clay,  loosened  by  frost 
or  by  percolating  water  and  its  own  weight,  slides  into  the  river,  and  is 
carried  down  stream.  Thus  a  nearly  perpendicular  bank  is  maintained, 
as  steep  as  the  imsupported  clay  will  stand.  Just  across  the  street,  at 
Concordia  cemetery,  the  same  bank  has  been  i^iotected  from  lateral 
erosion  by  a  high  fence  of  posts  and  planks  and  walls  of  loose  rock. 
While,  because  of  this  protection,  the  river  has  not  cut  outward  on  it" 
bend  at  the  cemetery,  it  has  trimmed  away  fully  25  feet  just  above  the 
bridge. 

Even  at  those  points  where  the  bluff  is  removed  from  the  river,  on  the 
opposite  side  of  its  valley,  the  slope  is  as  a  rule  steep  and  straight,  and 
the  valley  floor  at  its  base  is  often  marked  by  a  shallow  slough,  formerly 
occupied  by  the  river  when  it  trimmed  and  steepened  the  bluff.  (See 
contour  on  Fig.  17.) 

A  very  little  study  makes  it  clear  how  the  trench  has  been  cut  so  much 
wider  than  the  river  channel  and  everywhere  just  as  wide  as  the  meander 
belt.  When  the  river  first  found  its'  way  across  the  bay  plain,  a  surface 
exhibiting  frequent  inequalities  of  slope,  it  followed  many  crooks  and 
bends  much  like  those  of  the  present  course.  It  is  a  well  known  prin- 
^  ciple  that  at  each  bend  in  a  crooked  channel  the  current  of  river  swings 
'  toward  the  outside  of  the  curve  and  in  consequence  there  is  a  tendency 
for  the  river  in  time  of  high  water  to  trim  away  its  outer  bank.  This 
process  is  known  as  "lateral  planation."  At  the  same  time,  the  river  de- 
posits sediment  on  the  iiiside  of  the  curve  where  the  current  is  weak. 
The  combined  process  is  known  as  "cut  and  fill."  Now,  it  follows  from 
this  deflection  of  the  current  from  side  to  side  that  in  rounding  a  bend 
or  loop  the  river  does  most  of  its  cutting  on  its  down-valley  side  and 
most  of  its  filling  on  the  up-valley  side.  The  result  of  this  progressive 
growth  is  the  constant  migration  of  the  bends  down- valley.  Figure  31 
illustrates  the  effect  of  this  migration  on  the  outline  and  width  of  the 
valley.  As  the  bend  thus  shifts  its  position,  the  point  of  attack  against 
the  bank  likewise  shifts  down  valley,  so  that  a  straight  bluff  is  trimmed 
one  one  side  and  a  pointed  spur  developed  on  the  opposite  side.  (Fig.  21 
II.)  Slowly  this  spur  is  worn  away  as  the  upper  bend  encroaches  on  it 
(Fig.  21,  II,  III  and  IV),  and  by  the  time  this  second  bend  has  passed 
the  starting  point  of  its  predecessor  both  sides  of  the  valley  have  been 
trimmed  back.  There  remains  a  flat-floored,  straight-walled  trench, 
whose  width  corresponds  to  the  meander  belt  of  the  river.  It  necessarily 
follows,  also,  from  the  deflection  of  the  current  toward  the  outer  bank, 
that  as  the  river  cuts  downward  and  outward  the  bends  -will  increase  in 
size,  and  to  that  extent  the  meander  belt  will  be  widened.     While  the 


84 


THE    DES  PLAINES   VALLEY. 


[BULL.    NO      II 


bends  are  shifting  and  banks  are  being  trimmed,  the  filling  process  on 
the  inner  bank  covers  the  floor  of  the  valle}'  with  stratified  sediments 
and  a  flood-plain  is  formed — a  flat  valley  bottom,  usually  above  the 
river  level  but  submerged  whenever  the  river  is  swollen  by  rains  suffici- 
ently to  fill  its  channel  to  the  brim. 

During  low-water  stages  the  river  does  very  little  work.  It  is  too  weak 
to  carry  any  significant  amount  of  sediment.  Even  at  ordinary  stages 
the  river  works  slowly  and  laboriouslv :  but  during  floods,  when  the 
volume  of  the  stream  is  considerably  increased,  its  power  as  a  carrier  is 
enormously  increased,  and  it  is  then  that  the  cut-and-fill  process  is 
effective  and  flood-plains  are  constructed.  It  may  be  demonstrated  that 
the  transporting  power  of  a  river  varies  as  the  sixth  power  of  its  velocity 
and  that  its  velocity  varies  as  the  cube  root  of  the  volume,  if  the  shape 
of  the  channel  be  disregarded.    In  other  words,  the  carrying  power  varies 


III 


IV 


Fig.  21.  Diagrams  showing  the  development  of  a  straight  waUed,  flat  floored 
valley,  by  the  trimming  away  of  spurs  as  the  bends  of  the  stream  migrate  down- 
valley.  The  river  is  flowing  in  the  direction  of  the  arrow.  Four  stages  are 
shown.  In  I  al,  bl,  ci,  are  three  bends,  which  lie  between  three  alternating 
spurs,  X,  y,  z.  The  valley  bottom  is  narrow — no  wider  than  the  stream.  In  II  the 
tendency  of  the  stream  to  cut  on  the  down-valley  side  of  each  bend  has  shifted 
al,  h\,  and  ci  to  the  positions  ai,  hi,  ci,  leaving  stretches  of  straight  valley  walls, 
ol-a2,  bi-62,  cl-c2.  Across  the  river  at  each  bend  a  portion  of  the  up-valley  side 
of  each  spur,  x,  y,  z,  has  been  trimmed  away,  sharpening  these  spurs.  A  flat  floor, 
of  variable  width  (un-shaded)  has  thus  been  produced.  In  III  the  process  has  con- 
tinued. The  bends  have  migrated  down-valley  to  a3,  63,  c3.  The  stretches  of 
straight  valley  wall  have  been  lengthened,  ai-o3,  bi-&3,  cl-c3.  The  spurs  x,  y.  z, 
have  been  half  consumed  by  the  trimming  away  of  their  up-valley  sides.  The 
valley  floor  has  been  much  widened.  In  IV  a  still  later  stage  has  been  reached 
The  bend  a  has  shifted  down-valley  nearly  to  the  position  c,  extending  the  straight 
wall  al-a4  nearly  far  enough  to  consume  the  spur  y.  This  spur  is  now  very  blunt, 
and  will  be  wholly  consumed  by  the  time  bend  a  has  migrated  down-valley  to  the 
very  position  which  the  next  bend  below  it,  c,  originally  had.  The  other  spurs, 
x  and  z,  have  been  similarly  blunted,  and  will  soon  be  consumed.  The  valley  will 
then  be  straight  sided,  flat  floored,  and  as  broad  as  the  swing  of  the  bends,  i.  e.,  as 
the   meander   belt  of  the   river. 

as  the  square  of  the  volume.  If,  then,  the  flood  volume  of  a  river  is 
eight  times  its  normal  volume,  its  velocity  is  twice  as  great,  and  it  \% 
able  to  move  fragments  sixty-four  times  as  large  as  at  the  ordinary  stage. 
The  extreme  low  water  volume  on  the  Des  Plaines,  as  measured  at 
Riverside,  in  1887  was  4  cul)ic  feet  per  second;  the  flood  volume  of  the 
same  year,  10,324  cubic  feet.  AYhat  an  enormous  difference,  therefore, 
exists  in  the  carrying  power  and  sculpturing  power  of  the  river  between 
these  extreme  stages!     We  may  well  believe,   then,  that  just  as  the 


GOLDTHWAiT.]  HISTORY   OF   THE   UPPER    DES  PLAINES.  85 

average  yearly  flood  greatly  exceeds  the  ordinary  river  stages  in  its  work- 
ing capacity,  the  occasional  extremie  flood  greatly  exceeds  the  normal 
flood  in  its  destructive  and  constructive  work.  Although  extreme  floods 
commonly  occur  only  once  in  several  years,  and  at  irregular  intervals, 
the  flood-plains  which  they  build  are  usually  very  prominent  features 
of  the  valley.  During  the  interval  between  extreme  floods  (usually  5  to 
10  3'ears  in  the  case  of  the  Des  Plaines),  the  normal  yearly  floods  permit 
the  partial  destruction,  of  the  high-level  flood-plain  and  the  development 
of  a  lower  floor  at  the  level  of  ordinary  high  water.  The  erosion  of  the 
river  along  the  banks  of  its  channel  aids  somewhat  in  tearing  down  the 
high-level  plain;  but  before  the  upper  flood-plain  has  been  wholly  de- 
stroyed by  lateral  planation,  another  flood  of  imusual  proportions  occurs, 
and  the  high  flat  is  reconstructed.  One  of  the  most  striking  features  of 
the  Des  Plaines  trench  is  a  terrace  which  stands  several  feet  above 
ordinary  high  water  and  is  covered  only  by  extreme  floods  once  in  several 
years.  The  infrequency  of  submergence  of  this  terrace  is  shown  by  the 
fact  that  many  picnic  groves  with  their  small  buildings,  and  a  group  of 
cottages  at  the  Methodist  camp  grounds  at  Des  Plaines  are  located  upon 
it.  Earely  do  the  spring  freshets  rise  high  enough  to  cover  it,  but  when 
they  do  much  damage  is  done.  Stretches  of  bottom  land  a  few  feet  lower 
than  the  terrace  and  alwavs  between  it  and  the  river  mark  the  level  of 
ordinary  annual  floods. 

The  Des  Plaines  river  illustrates  remarkably  well  the  features  just 
described  and  figured.  Migrating  bends,  straight-trimmed  bluffs  and 
broad  flood-plain  are  exhibited  especially  well  between  Maywood  and 
Eiverside.  (Figure  17.)  The  bends  of  the  Des  Plaines  are  as  a  rule 
obtuse  rather  than  acute,  hence  the  trench  formed  as  they  have  sunk 
and  moved  down  valley  is  rather  narrow  when  compared  with  the  few 
places  where  the  bends  are  more  circular  (e.  g.  the  S-shaped  bend  two 
miles  above  Maywood  and  a  series  of  curves  above  Des  Plaines  village). 
There  the  more  rapid  enlargement  of  the  curves  together  with  their 
down-valley  migration  has  formed  a  trench  400  to  500  yards  wide. 

When  studied  in  connection  with  a  large  river  like  the  Missouri  or 
Mississippi,  the  Des  Plaines  is  found  to  be  deficient  in  the  regularity 
and  symmetry  of  its  bends.  Close  study  will  also  show  that  its  valley 
is  not  wide  enough  in  proportion  to  its  channel  to  compare  with  rivers 
which  have  reached  an  advanced  or  mature  stage  of  development.  The 
widening  of  a  river  valley  continues  as  a  rule  until  the  meander  belt  is 
at  least  sixteen  times  as  wide  as  the  river  channel.  By  that  time  the 
crooks  have  turned  into  loops  of  great  beauty  and  symmetry,  and  the 
trimming  of  the  bank  no  longer  occurs  at  every  bend.  The  meander 
becomes  more  and  more  looped,  the  inclosed  lobes  of  flood-plain  match- 
ing together  in  dove-tailed  fashion.  The  necks  of  the  pear-shaped 
spurs'  grow  narrower  and  narrower  by  the  cut-and-fiU  process,  until  at 
last  (usually  in  time  of  flood)  the  river  cuts  through  the  neck,  gaining 
a  shorter  course,  and  the  long  loop  is  abandoned,  becoming  either  a 
slough  or  an  ox-bow  lake.  These  old  "meander  scars"  are  gradually 
effaced  by  deposits  of  sediment  during  subsequent  floods. 


86  THE   DES  PLAINES   VALLEY.  [bull.  no.  11 

As  regards  its  stage  of  development,  therefore,  the  Des  Plaines  may 
be  called  a  youthful  river.  In  its  infancy  a  crooked  stream,  running 
along  the  newly  exposed  bay  plain,  it  was  enabled  to  lower  its  channel, 
and  in  so  doing  sent  a  succession  of  loops  moving  down  valley.  By  them 
its  valley  floor  has  been  widened  and  its  valley  walls  trimmed  back.  It 
is  still  at  work  at  these  tasks,  broadening  its  valley  by  lateral  planatiou, 
seeking  to  gain  a  floor  sufficiently  wide  on  which  to  turn  and  twist  in 
closed  loops  like  the  larger  and  older  "father  of  rivers"  to  which  it  is 
tributary.  No  longer  exactly  "young,"  it  is  still  "youthful."  Another 
interval  of  time,  as  long  probably  as  that  already  elapsed  in  the  river's 
history,  will  be  required  for  the  river  to  reach  full  maturity. 

DEVELOPMENT    OF    TRIBUTARIES. 

The  development  of  tributaries  to  the  upper  river  has  already  been 
partly  discussed.  The  larger  tributaries,  like  Salt  creek  and  Higgins 
creek,  which  head  on  the  Valparaiso  moraine  and  cross  the  old  floor  of 
Des  Plaines  bay  to  reach  the  main  river,  have  already  been  spoken  of. 
They  are  conseq'ient  upon  the  drift  surface,  having  followed  the  guid- 
ance of  initial  slopes.  Along  their  lower  courses  the  tributaries  south 
of  Franklin  Park  were  extended  and  engrafted  on  the  Des  Plaines  as 
the  bay  plain  emerged,  at  the  close  of  the  Glenwood  stage  of  Lake  Chi- 
cago. As  previously  remarked,  these  tributaries  are  confined  almost 
wholly  to  the  west  side  of  the  Des  Plaines.  The  low  till  ridge  that  forms 
the  eastern  side  of  the  valley  does  not  gather  and  shed  enough  water  to 
support  permanent  streams  of  any  considerable  length. 

Some  of  the  larger  of  these  tributary  creeks,  near  where  they  join  the 
Des  Plaines,  have  a  remarkably  mature  aspect ;  for  they  meander  broadly, 
with  horse-shoe  shaped  loops.  One  of  the  most  accessible,  as  well  as  one 
of  the  prettiest  examples  is  the  creek  which  enters  the  river  north  of 
May  wood,  opposite  Theiler's  park.  (See  Figure  17.)  Its  valley  floor, 
unlike  that  of  the  Des  "Plaines,  is  much  wider  than  the  meander  belt, 
and  the  meanders  approach  in  shape  those  of  the  Mississippi.  In  these 
respects,  the  tributary  looks  more  mature  than  the  trunk  river.  Such  a 
condition  is  quite  abnormal  and  demands  explanation;  for  we  should 
expect  the  trnnlv  stream  to  have  reached  a  more  advanced  stage  of  de- 
velopment than  any  of  its  tributaries.  The  explanation  seems  to  be 
found  in  the  influence  which  strong  floods  of  the  main  river  have  on  the 
flood  plain  of  the  branch  stream.  It  is  very  apparent  that  when  the  Des 
Plaines,  gathering  a  large  volume  from  its  long  basin  during  a  spring 
thaw  or  a  heavy  rain,  is  swollen  and  overtops  its  flood  plain,  it  invades 
the  lower  end  of  the  tributary  valley,  backing  the  waters  up.  In  this 
bay-like  extension  of  the  trunk  valley,  during  the  flood,  silts,  chiefly 
from  the  main  river,  may  be  laid  down  and  a  flood  plain  built  up  to 
the  back-water  level.  A  flood-plain  constructed  imder  such  conditions 
would  be  flatter  than  one  formed  by  the  tributary  itself,  flowing  down- 
grade into  the  main  river;  and  on  such  an  over-flattened  plain,  after  the 
flood  subsided,  the  tributary  would  be  apt  to  meander  more  widely  than 
on  the  sloping  floor  of  its  upper  course.     The  fact  that  the  "mature" 


GOLDTHWAIT.J  HISTOEY   OF    THE   UPPEE    DES  PLAINER.  87 

loops  seem  to  be  restricted  to  the  lower  courses  of  the  tributaries  favors 
the  idea  that  they  are  due  to  back-water  influence. 

This  class  of  tributaries  might  be  called  "original,"  to  distinguish 
them  from  another,  newer  group  of  "secondary"  origin. 

The  manner  in  which  the  second  class  of  tributaries  start  to  grow  may 
be  studied  to  advantage  wherever  the  main  river  is  bordered  by  a  freshly 
trimmed  bank ;  as,  for  instance,  at  the  Madison  street  bridge.  It  will  be 
observed  here  that  the  clay  slope  is  carved  by  innumerable  little  gullies, 
the  work  of  recent  rains.  Such  of  the  gullies  as  chance  to  find  an  ad- 
vantageous place  for  headward  growth,  either  becaase  of  softer  ground 
structure  than  their  neighbors  or  because  of  an  initial  depression  near 
their  heads,  from  which  they  may  receive  more  than  an  equal  share  of 
the  run-off,  will  grow  more  rapidly  than  those  on  either  side.  In  the 
incipient  stages,  such  differences  in  rate  of  growth  are  slight;  the  ad- 
vantages are  small,  and  largely  accidental.  The  presence  of  a  tree  root 
that  will  turn  the  rain  wash  away  from  one  gully  and  towards  its  neigh- 
bor may  be  of  prime  importance  in  determining  which  shall  grow.  With 
growth,  both  lateral  and  headward,  the  favored  gullies  rapidly  swallow 
up  or  dwarf  their  neighbors.  Natural  selection  operates  as  truly  here 
as  in  the  realm  of  life.  Of  the  hundreds  of  gullies  on  a  newly  rain- 
carved  bank,  only  one  or  two  are  destined  to  grow  to  conspicuous  size; 
and  but  one  out  of  many  thousand  will  develop  into  a  large  ravine.  It 
should  further  be  said  that  of  the  gullies  carved  by  side  wash  down  a 
river  bank  there  is  wholesale  destruction  at  the  hands  of  the  river  itself; 
for  it  as  a  rule  trims  away  its  bank  faster  than  most  of  its  side  gullies 
wear  back  their  heads.  This,  together  with  the  competition  among  the 
gullies  themselves,  explains  the  delay  in  the  development  of  tributary 
ravines. 

ISTorth  of  the  Madison  street  bridge,  in  the  picnic  grove  and  woods, 
may  be  found  gullies  of  "secondary"  tributaries  in  various  stages  of 
growth.  Short,  steep,  V-shaped  gullies  with  bare  sides  occur  close  to  the 
bridge,  where  the  freshly  trimmed  river  bank  is  being  scoured  by  rains. 
About  an  eighth  of  a  mile  north  of  Madison  street  is  a  small  ravine, 
which  is  some  300  yards  long  and  at  its  mouth  is  about  20  feet  deep. 
It  has  no  branches,  and  is  remarkably  straight,  yet  towards  its  mouth 
it  bends  back  and  forth  between  a  set  of  interlocking  spurs,  similar  to 
those  described  on  pages  83-8-i.  Besides  the  examples  near  Madison 
street,  there  are  well  developed  "secondary"  tributaries  in  the  northeast 
part  of  Mavwood,  two  of  which  are  shown  by  contours  on  the  map,  Fig. 
18. 

These  "secondary"  tributaries,  formed  by  the  headward  growth  of 
lateral  gullies,  are  few,  short,  and  exceedingly  simple  in  plan.  They 
have  few  or  no  branches.  Like  other  features  of  the  valley  they  are 
marks  of  the  youthful  condition  of  the  Des  Plaines  system. 


88  THE    DES  PLAINES    VALLEY.  [BULL.  no.  11 


CHAPTER  VII. 


FLOODS  ON  THE  DES  PLAINES  EIVER. 

THE  UPPER  RIVER. 

The  Des  Plaines  river  is  subject  to  floods  of  unusually  long  duration, 
as  compared  with  other  rivers  of  its  size.  Each  spring,  as  the  snow  melts 
rapidly  out  of  its  basin,  the  river  is  swollen  by  the  additional  volume, 
and  rises  several  feet  above  its  normal  level.  A  portion  of  the  valley 
floor  is  thus  flooded  for  days  or  even  weeks. 

In  his  paper  on  ''The  Illinois  river  basin  in  its  relations  to  sanitary 
engineering,"^  Mr.  L.  E.  Cooley  expresses  the  view  that  the  peculiar 
shape  of  the  basin — narrow  from  east  to  west,  and  sixty  miles  long  from 
north  to  south  above  Eiverside  (See  Fig.  1)  makes  the  floods -on  the 
Des  Plaines  last  longer  and  rise  less  than  they  would  in  an  equally 
large  basin  of  different  shape.  When  a  warm  spell  comes  in  the  spring, 
attended  perhaps  by  rains,  the  snow  and  ice  are  rapidly  melted  from 
the  frozen  ground,  and  on  all  sides  water  runs  down  the  slopes  into 
the  river.  The  melting  begins  a  little  sooner  at  the  south  end  of  the 
basin  and  advances  northward  up  the  valley  to  the  head-waters.  Ac- 
cordingly, "after  heavy  precipitation  the  maximum  flow  comes  from 
the  immediate  body  of  the  watershed,  while  the  flow  from  the  head- 
waters will  come  in  to  sustain  the  volume  and  to  prolong  the  flood. 
The  melting  of  the  snow  in  the  north  portion  of  the  basin  will  maintain 
the  flow  for  several  days  after  it  has  melted  and  run  away  from  the 
south  portion." 

In  this  respect  the  Des  Plaines  river  is  the  antithesis,  on  a  small 
scale,  of  the  Eed  river  of  Minnesota  and  Dakota,  which  runs  towards 
the  north  for  several  hundred  miles,  and  chiefly  on  that  account  is  sub- 
ject to  very  high  and  destructive  floods.^ 


1  Appendix  to  a  report  on  "Water  Supplies  of  Illinois."  Preliminary  report  to 
the   Illinois   State   Board   of  Health,    pp.    49-81.    1889. 

2  One  of  these  occurred  in  the  sprin.a:  of  1897.  During-  th?  preceding-  -winter 
several  feet  of  sno-w  had  accumulated  on  the  ground,  around  the  head-waters  of 
Red  river.  Early  in  April,  in  the  course  of  only  two  or  three  days,  all  this  sno-w 
•was  melted  off  by  a  -warm  -n-ave.  The  immense  volume  of  v^ater  thus  let  loose 
quickly  found  its  way  over  the  frozen  g-round  into  the  river,  swelling-  it  beyond  all 
proportions.  Farther  down  the  river,  i.  e..  farther  north,  where  the  arrival  of  the 
warm  wave  was  somewhat  delayed,  the  ice  had  only  begtin  to  break  up  when  the 
flood  and  floating  ice  from  the  headwaters  were  precipitated  upon  it.  Ice  jams 
were  formed,  and  the  Red  river  was  dammed  back,  at  Fargo  and  Morehead,  until 
it  was  12  miles  wide. 


GOLDTHWAIT.]  FLOODS   ON   THE    DES  PLAINES.  89 

While  the  meridional  length  of  .the  Des  Plaines  basin  is  an  interest- 
ing fact,  when  seen  in  this  light,  and  while  it  may  operate  to  some 
extent  in  prolonging  floods,  it  seems  hardly  likely  that  because  of  the 
difference  of  latitude  alone  the  snow  would  melt  sooner  at  its  south  end 
than  at  its  north  end.  The  sun's  rays  are  hardly  one  degree  higher 
at  the  former  than  at  the  latter.  Certainly  the  difference  would  not 
cause  a  delay  of  several  days  in  the  melting  process.  The  explanation 
of  the  delay  in  the  northern  portion  of  the  basin,  about  the  head- 
waters, is  probably  to  be  found  in  the  greater  acreage  of  forest  there  and 
the  greater  diversity  of  surface,  affording  more  frequent  shaded  slopes. 

Mention  has  been  made  of  the  spring  freshet  of  1674,  in  which  the 
Des  Plaines  discharged  so  much  water  eastward  towards  Chicago  that 
Marquette  and  his  two  companions  were  forced  to  abandon  their  hut 
heside  the  Chicago  river,  and  were  enabled  to  cross  the  divide  in  canoes 
a  few  days  later.  Another  flood  of  this  sort,  accentuated  by  ice  jams 
near  Summit,  caused  much  damage  to  shipping  and  bridges  on  the 
Chicago  river  in  1849. 

One  of  the  most  extraordinary  floods  of  which  there  are  accurate 
measurements  was  in  April,  1881.  Mr.  Cooley  tells  of  it  in  these 
words.^  "The  flood  maintained  its  height  for  nearly  four  days,  and 
lasted  about  twenty-one  days.  The  ground  was  practically  saturated 
when  winter  set  in,  and  about  one  foot  of  water  in  the  shape  of  ice  and 
show  accurnulated,  and  all  ran  out  or  melted  during  three  weeks,  at  a 
temperature  a  little  above  freezing  point  and  without  material  rain. 
The  southern  portion  of  the  watershed  was  entirely  bare  before  the 
northern  snows  began  to  melt.  For  this  reason,  the  flood  volume  held 
measurably  constant  even  toward  the  sources  of  the  stream,  until  the 
snow  at  headquarters  began  to  be  exhausted.  The  conditions  presented 
in  this  flood  are  of  extraordinary  occurrence  only.''  On  April  21st 
the  flood  reached  its  maximum  height  at  Eiverside,  the  discharge  over 
the  dam  amounting  to  13,500  cubic  feet  per  second.  The  river  here 
was  nearly  six  feet  above  its  low-water  level.  At  the  Ogden  dam  the 
river  rose  more  than  seven  feet  above  its  low-water  mark,  giving  an 
overflow  there  3y2  feet  in  depth,  so  that  a  considerable  part  of  the  flood 
waters  found  their  way  to  the  Mud  Lake  district  and  Lake  Michigan 
instead  of  down  the  lower  Des  Plaines.  The  proportion  of  water  which 
"turned  eastward  was  abnormally  great  on  April  9th  and  10th,  because 
of  an  ice  gorge  on  the  river.  Nearly  all  the  water  that  passed  Eiverside 
on  these  two  days  was  diverted  towards  Lake  Michigan.  At  Kedzie 
avenue  the  volume  flowing  through  the  Ogden  ditch,  from  the  flooded 
slough  into  the  Chicago  river,  was  as  follows: 

Feb.  10th 7,800   cu.   ft.   per  second. 

(cf.  with  the  8,00  feet  at  Riverside.) 

Feb.  11th 4,636  cu.  ft.  per  second. 

Feb.  14th 1,625  cu.  ft.  per  second. 

Feb.  18th 4,000  cu.  ft.  per  second. 

Feb.   9th    3,042  cu.  ft.  per  second. 


1  Op.    cit.,    p.    74. 


90  THE   DES  PLAINES  VALLEY.  [BULL.  no.  11 

The  figures  determined  at  three  stations  show  that  the  flood  was 
double,  decreasing  between  the  10th  and  16th  and  rising  again  on  the 
19th.  Regarding  the  effect  of  the  overflow  across  Ogden  dam  in  dimin- 
ishing and  regulating  the  flood  along  the  lower  Des  Plaines,  Mr.  Cooley 
says:^  "When  the  water  in  the  Des  Plaines  stands  at  the  crest  of  the 
dam,  the  flow  down  the  Des  Plaines  is  800  to  1,000  feet  per  second, 
depending  upon  whether  the  water  is  falling  or  rising,  or  on  the  con- 
dition of  vegetation  in  the  '12-mile  level.'  Above  this  volume,  the 
proportion  escaping  to  Chicago  increases  rapidly  with  the  height  of 
flood,' and  for  this  reason  the  floods  passing  Joliet  are  more  uniform  in 
volume,  one  year  with  another,  than  at  Eiverside."  In  large  floods 
fully  half  the  water  goes  over  the  dam  of  Lake  Michigan.  The  crest 
of  the  dam  is  11.7  feet  above  the  lake  (Chicago  datum  for  Lake  Mich- 
igan, 580  feet  above  the  sea.)  In  low  water  the  river  is  3.7  feet  below 
the  dam. 

Another  unusual  flood  occurred  early  in  Februar}^  1887,  reaching  a 
maximum  height  at  Eiverside  on  the  Oth.^  The  volume  of  discharge 
as  measured  at  Eiverside  and  Joliet  on  different  days  is  as  follows: 

Riverside.  Joliet. 

Cu.  tt.  per  sec.    Cu.  ft.  per  sec. 

Feb.      9th 10,324  

Feb.    10th 8,000  

Feb.    11th 7,000  5,775 

Feb.    16th 2,000  1,460 

Feb.    19th 5,374  5,385 

Comparing  figures  at  the  two  stations  for  the  11th  and  the  16th,  it 
is  seen  that  a  large  fraction  of  the  volume  which  passed  Eiverside  escaped 
over  the  Ogden  dam  to  Lake  Michigan,  diminishing  the  flood  at  Joliet 
very  materially. 

According  to  Mr.  Cooley,  an  extraordinary  flood,  with  discharge 
of  upwards  of  10,000  cubic  feet  per  second  at  Eiverside,  occurred  every 
five  or  six  years  between  1840  and  1890.  Of  the  fifty-three  floods 
that  occurred  between  1834  and  1890,  thirty-eight  were  in  February, 
March,  or  April,  and  the  majority  associated  with  the  spring  breakup. 
"The  ordinal^  yearly  flood  as  deduced  from  marks  on  the  Lyons  dam 
is  6,000  to  7,000  cubic  feet  per  second. "* 

At  the  Fullersburg  dam  on  Salt  creek  several  extraordinary  floods 
have  given  a  discharge  of  about  3,800  cubic  feet  per  second.  On  Feb- 
ruary 10th,  1887,  the  volume  was  2,860  cubic  feet.  If  the  volumes  of 
floods  on  Salt  creek,  compared  with  those  on  the  Des  Plaines,  were  in 
direct  proportion  to  the  areas  of  the  respective  basins,  the  flood  at 
Eiverside  on  February  10th  should  have  been  over  16,000  cubic  feet 
instead  of  10,324.  The  failure  of  the  flooded  Des  Plaines  to  attain 
a  volume  proportional  to  that  of  Salt  creek  is  thought  by  Mr.  Cooley 
to  be  due  to  the  greater  meridional  length  of  the  main  basin,  in  which 
the  melting  of  snow  advances  northward  day  by  day,  prolonging  and 
equalizing  the  flood. 

1  Op.   cit,   p.   73. 

2  The  source  of  the  information  here  pre-sented,  on  the  floods  of  1881  and  1887, 
is   Mr.   Cooley's   report,   previously   cited. 

3  Op.  cit.,  p.   73. 


GOLDTHWAIT.]  FLOODS    ON    THE    DES  PLAINES.  91 

The  dry-weather  volume  of  the  Des  Plaines  is  extremely  small ;  for 
the  river  has  not  cut  clown  its  bed  sufficiently  below  permanent  ground- 
Water  level,  and  must  get  its  supply  almost  wholly  from  surface  run-off. 
In  1887  the  discharge  at  Eiverside  was  diminished  to  four  cubic  feet 
per  second,  as  contrasted  with  10,324  feet  in  the  February  flood  of  the 
same  year.  For  five  months  the  discharge  did  not  exceed  seventeen  feet 
per  second.  Although  the  river  has  been  known  to  be  even  lower  than 
this  it  has  never  run  dry.  Salt  creek,  however,  was  dry  at  Fullers- 
burg  in  1887. 

The  effects  of  settlement  of  the  basin  in  changing  the  height  and 
direction  of  the  floods  from  their  original  and  natural  condition  has 
been  pointed  out  by  Mr.  Cooley.  During  the  settlement  of  the  valley, 
the  clearing  away  of  timber  and  the  draining  out  of  the  bogs  and 
marshes  by  systematic  trenches  largely  destroyed  the  natural  reservoirs 
and  regulators  of  floods,  allowing  a  more  immediate  run-off;  conse- 
quently the  floods  now  are  higher  and  of  shorter  duration.  The  flow 
of  the  river  during  the  year  is  less  uniform,  and  low-water  lasts  much 
longer  than  formerly.  These  effects  are  even  more  strongly  felt  on 
the  Kankakee  river,  where  broad  marsh  lands  have  been  reclaimed. 

THE  LOWER  RIVER. 

On  account  of  the  usual  diversion  of  a  large  fraction  of  the  flood 
watere  by  the  Ogden  dam  at  Summit,  the  floods  which  are  conspicuous 
above  Summit  are  usually  of  minor  concern  to  the  property  owners  on 
the  lower  course  of  the  river.  As  the  flood  rises  higher  and  higher 
above  the  Ogden  dam,  a  larger  and  larger  fraction  of  it  overflows 
toward  Lake  Michigan.  So,  at  Lemont,  Lockport,  and  Joliet  the  floods 
as  a  rule  are  lower  than  at  Eiverside,  and  more  uniform  from  year  to 
year.  The  normal  extreme  flood  at  Eiverside  (as  computed  by  Mr. 
Cooley)  is  nearly  twice  that  at  Joliet  (12,000  and  6,300  cubic  feet  re- 
spectively.) 

■  Measurements  on  the  dam  at  Joliet  determine  discharges  during  ex- 
traordinary floods  as  follows : 

1877   (April     7th) 6,410  cu.  ft.  per  second. 

1881   (April    21st) 6,550  cu.  ft.  per  second. 

1883   (Feb.    16th) 6,370  cu.  ft.  per  second. 

1887   ( Feb.    11th ) 5,775  cu.  ft.  per  second. 

In  the  flood  of  April,  1881,  the  highest  for  thirty-three  years  (up  to 
1890),  the  water  was  3.75  feet  high  on  the  Jackson  street  dam  at 
Joliet.  This  city,  however,  does  not  always  escape  floods.  Local  cloud- 
bursts, flooding  the  tributaries  east  and  north  of  the  city  on  the  Val- 
paraiso moraine,  occasionally  cause  much  destruction  of  property  in 
Joliet.  One  of  these  occurred  on  August  10,  1867,  which  flooded  a  part 
of  the  city  and  in  a  few  hours  caused  much  damage. 

The  worst  flood  within  the  memory  of  the  townspeople  occurred  at 
about  midnight  June  2nd  and  3rd,  1902.  A  storm  began  about  9  :00 
o'clock  in  the  evening,  increasing  to  a  heavy  downpour  which  was  ac- 
companied by  hail.     Motormen  were  driven  from  the  fronts  of  their 


92  THE   DES  PLAINES   VALLEY.  [bull.  no.  11 

cars  by  the  hailstones.  By  midnight  the  water  in  the  drainage  canal  had 
risen  several  feet.  The  old  slough  which  lies  between  Eastern  avenue 
and  the  Alton  railway  (in  the  heart  of  the  city)  was  a  raging  torrent. 
The  northeast  portion  of  the  city  north  of  Columbia  street  became  a 
temporary  lake.  The  greatest  inundations,  however,  were  along  Hick- 
ory creek,  in  the  section  known  as  Brooklyn.  The  water  poured  over  the 
Hickory  creek  dam  at  the  red  mill  three  or  four  feet  deep,  and  a  por- 
tion of  the  dam  at  last  gave  way.  The  Union  elevator  was  surrounded 
by  a  lake,  and  its  low^er  portion  flooded;  but  no  grain  was  destroyed. 
A  bridge  near  by,  on  the  Michigan  Central  spur  track,  was  washed  out. 
On  Brooklyn,  Iowa,  and  Mississippi  avenues,  the  waters  flooded  the 
sidewalks  and  poured  through  basement  windows,  filling  cellars  and  in 
some  cases  invading  even  the  living  rooms  on  the  ground  floor.  Houses 
were  partially  wrecked  as  their  foundations  were  undermined.  One 
small  house  was  swept  along  several  blocks  and  lodged  against  the 
Second  avenue  bridge.  The  darkness  of  the  night  magnified  the  con- 
fusion and  horror  of  the  scenes.  People  turned  out  long  before  daylight 
witb  boats,  ladders,  and  rigs  for  the  relief  of  the  imprisoned  ones,  and 
the  fire  and  police  departments  responded  to  the  emergency.  On  Mc- 
Donough  street  a  horse  and  wagon  carrying  six  people  to  some  place 
of  refuge  was  overwhelmed  by  the  current,  and  two  of  the  passengers 
were  drowned.  Many  others  had  narrow  escapes  from  drowning.  It 
was  feared  that  the  big  dam  at  Jackson  street  would  go  out,  but  it  did 
not. 

The  railways  were  among  the  heaviest  losers  from  this  flood.  The 
Eock  Island  railway  bridge  over  the  Des  Plaines  swung  17  inches  out 
of  position,  a  supporting  pier  being  washed  out.  On  the  Michigan 
Central  the  transfer  yards  were  destroyed.  The  car  sheds  of  the  street 
car  company  were  flooded,  and  the  motors  of  many  cars  ruined  by 
water.  Stove  works  and  mills  sufl^ered  likewise  from  inundation.  Mer- 
chants within  the  lower  portion  of  the  city  lost  heavily  of  goods  stored 
in  basements.  A  local  newspaper  estimated  the  damage  at  over  $500,000. 
For  several  hours  Joliet  was  cut  off  from  the  outside  world.  No  trains 
passed  through  the  city  until  the  following  morning. 

At  Lockport  the  small  creeks  which  drain  the  bluffs  were  veritable 
torrents,  tearing  away  fences,  bridges,  and  even  stone  walls;  destroying 
gardens  and  sweeping  the  debris  into  the  Illinois-Michigan  canal  so 
fast  that  it  was  choked  up  and  overflowed  its  banks.  In  this  way  the 
west  side  of  the  town  was  flooded  and  the  colored  people  driven  from 
their  homes.  The  Barrows  Lock  company  suffered  damages  of  about 
$2,000.  At  Eomeo  the  quarries  were  filled  to  the  brim,  and  the  farmers 
lost  crops  and  young  stock.  The  Santa  F'e  tracks -were  blocked  until  the 
following  evening,  delaying  the  mails: 

There  were  two  washouts  on  the  Eock  Island  railway  above  Joliet,  on 
Hickory  creek.  At  New  Lennox,  bridges  and  culverts  were  damaged  to 
the  extent  of  $1,500.  At  a  washout  on  the  track  just  east  of  the  depot 
the  night  train  on  the  Eock  Island  barely  escaped  a  wreck.  The  floo(' 
of  1902,  the  highest  for  many  years,  was  quite  abnormal,  occurring,  a; 
it  did,  in  June,  in  response  to  a  local  cloud-burst. 


STATE    GEOLOGICAL   SURVEY. 


BULL.   NO.    11,   PL.    9. 


*  Bi.  - 

^HBfll^       ^  '^^H^^^^^l 

^  - 

Effects   of  a   Recent   Flood   on   Hickory   Creek. 


GOLDTHWAIT.]  FLOODS   ON    THE    DES  PLAINES.  98 

A  more  typical  flood  took  place  on  January  19,  1907,  wlien,  during  a 
temporary  thaw  and  rain,  Hickory  creek  overflowed  its  banks  through 
the  city  and  the  water  on  the  Des  Plaines  rose  within  a  few  inches  of 
the  top  of  the  embankment.  Weak  points  on  the  retaining  wall  above  the 
Economy  plant  were  hastily  reinforced,  and  the  dam  at  the  controlling 
works  was  raised  to  lessen  the  flow.  Brooklyn  was  again  under  water; 
cellars  were  flooded,  furnace  fires  extinguished,  and  fuel  rendered  use- 
less. The  storm  was  accom})anied  by  high  winds  that  wrecked  the  houses 
where  foundations  had  been  loosened  by  the  floods.  Furniture  and 
personal  property  was  hurriedly  moved  to  places  of  safety.  The  climax 
of  the  flood  was  reached  about  8  p.  m.,  when  a  cold,  wave  bc^gan  to  check 
the  discharge.  The  waters  slowly  fell  as  the  little  headwaters  and  side- 
slopes  of  the  Hickory  creek  system  were  gradually  frozen.  At  the  same 
time  the  occupants  of  many  houses  found  their  cellars  filled  with  3  to 
5  feet  of  water  and  their  fuel  inaccessible.  Sutt'ering  from  cold  sup- 
plemented the  direct  injury  from  floods.  All  the  railways  were  blocked. 
At  several  places  between  Joliet  and  New  Lennox,  the  Uock  Island 
tracks  were  under  water. 

After  such  a  flood  as  this  there  are  many  interesting  things  to  observe 
on  the  recently  submerged  flood-plain.  Some  of  the  drift-wood  and  rub- 
bish which  was  swept  down  the  valley  has  been  caught  by  bushes  and 
trees  that  grow  on  the  flood-plain,  forming  great  bunches  of  floatsam  as 
high  as  the  flood  level.  On  Hickory  creek  below  New  Lennox,  where 
the  photographs  (Plate  9)  were  taken,  two  months  after  the  flood  of 
January,  1907,  the  rubbish  heaps  indicated  a  rise  'of  the  water  7  feet 
above  ordinary  level.  In  the  lee  of  each  of  these  rubbish-laden  bushes  the 
turf  on  the  floor-plain  had  been  gullied  out  by  the  eddying  currents. 
A  lofty  elm  tree  a  little  bekw  New  L-ennox  had  been  swept  down 
stream,  its  branches  trailing  along  behind  it  and  ripping  long  grooves 
in  the  flood-plain  surface.  (See  Plate  9,  A.)  Close  to  New  Lennox  sta- 
tion a  smaller  type,  stranded  in  the  bed  of  Hickor}-  creek,  had  within  two 
months  after  the  flood  caused  the  construction  of  a  considerable  bar  of 
sand  in  mid-channel.  The  scattering  of  fresh  shingle  over  large  tracts 
of  the  grassy  floor-plain  in  some  places  and  the  tearing  away  of  the  old 
structures  in  others,  after  floods  like  this,  shows  how  far  from  stable  is 
the  course  of  the  river  channel. 

Eecent  ditching  of  marshy  areas  at  the  head  waters  of  Hickory  creek, 
near  Tinley  park  and  elsewhere,  in  order  to  make  them  available  for 
farming,  may  be  expected  to  affect  the  height  and  duration  of  floods  as 
already  discussed  in  the  preceding  section.  The  more  extensively 
swampy  conditions  are  replaced  by  definite  lines  of  drainage  the  faster 
will  the  run-off  occur.  Floods  will  rise  higher  but  they  will  not  last  so 
long. 


94  THE   DES   PLAINER   VALLEY.  [bull.  no.  11 


APPENDIX. 


SUGGESTIONS  FOE  FIELD  TEIPS. 

The  object  of  this  appendix  is  to  suggest  some  of  the  more  accessible 
and  more  interesting  localities  in  the  Des  Plaines  valley  where  physical 
features  may  be  studied  to  advantage  by  the  amateur  or  by  the  teacher 
-with  a  class.  The  catalog  is  by  no  means  an  exhaustible  one.  Every 
locality  has  its  features  of  peculiar  interest,  and  the  amateur  or  the 
teacher  will  naturally  find  and  study  those  which  are  nearest  at  hand. 
The  localities  listed  here,  however,  are  representative,  and  any  one 
of  them  might  form  the  subject  of  an  instructive  field  trip.  For  details 
and  for  descriptions  of  the  localities  and  the  features  noted  here,  refer- 
ence should  be  made  to  the  text  or  illustrations,  as  indicated  in  paren- 
thesis. Although  the  localities  are  classified  under  certain  subjects, 
such  as  "river  erosion/'  "old  shorelines  of  Lake  Chicago,"  etc.,  it  is 
needless  to  say  that  a  great  variety  of  features  may  be  studied  at  any 
locality,  and  only  the  most  conspicuous  or  most  interesting  of  these 
features  are  suggested  in  the  list. 

RIVER  EROSION. 

Certain  fundamental  studies,  such  as  the  observation  and  measure- 
ment of  velocity  of  the  current  (in  feet  per  mile)  during  low  water  and 
during  a  flood,  the  transportation  of  sediment,  etc.,  might  be  conveni- 
ently made  at  several  of  the  following  localities.  These  are  not  men- 
tioned among  the  features  cataloged  below :  . 

Maywood. — Northwest  part  of  town.  Meandering  and  lateral  planu- 
tion  of  the  Des  Plaines  river ;  broad  flood  plain ;  development  of  tribu- 
tary ravines;  a  peculiar  case  of  mature  condition  of  a  tributary,  with 
broad  open  valley  and  several  well  developed  meanders  of  the  true 
looped  form.     (pp.  83-86  and  Fig.  17.) 

Harlem. — Madison  street  bridge.  Broad  valley  of  the  Des  Plaines; 
flood  plain;  channel  close  to  left  bank;  destructive  lateral  planation 
opposite  Concordia  cemetery ;  development  of  gullies  along  bank  of  main 
river;  j'oung  ravine,     (p.  83  and  Fig.  17.) 

Riverside. — Peculiar  bend  of  the  Des  Plaines  river  around  the  Calu- 
met beach  ridge ;  ledges  in  its  bed  near  the  mouth  of  Salt  creek ;  Lyons 
dam,  for  development  of  water  power,     (pp.  4  and  5;  Fig.  19.) 


GOLDTHWAiT.]  SUGGESTIONS   FOR   FIELD   TRIPS.  95 

Joliet. — (a)  Reed's  woods.  Young  ravine;  narrow  flood  plain;  trim- 
ming spurs;  behavior  of  river  on  meanders;  development  of  tributary 
ravines  and  gullies;  their  headward  groyvth.  (pp.  60,  83-86;  Fig.  21; 
PL  7.) 

(&)  Sugar  creeTc.  Gorge  in  rock;  effect  of  joint  planes  on  shape  r>f 
walls;  waterfalls  and  pools,     (pp.  59,  60;  PL  2  B,  and  6.) 

(c)  Hichory  creel:,  below  old  red  mill;  and  Spring  creek  above  old 
wire  mill.  Outwash  terrace;  its  gravelly  constitution  and  stratified 
structure;  amount  of  excavation  since  the  ice  sheet  withdrew  from 
the -moraine  and  excavation  commenced;  arrangement  of  blocks  and 
pebbles  in  bed  of  river,  like  overlapping  shingles  on  a  roof;  effects  of 
recent  floods  on  pastures,  trees,  fences,  houses,  etc.  (pp.  59,  60;  Pis. 
5  A,  and  9.) 

'     GLACIAL  MORAINE. 

Ehnliurst,  or  Hinsdale. — Characteristic  swell-and-sag  topography; 
frequent  undrained  depressions.,     (p.  33.) 

Joliet. —  (a)  West  ridge,  crossed  on  the  Plainfield  road,  a  mile  north 
west  of  town.    Swell-and-sag  topography;  transverse  slough,     (p.  49.) 

(&)  East  end  of  McEnty  street,  a  half  mile  east  of  the  penitentiary. 
Swell-and-sag  topography;  pond  in  an  enclosed  depression;  section  of 
the  moraine,  showing  bowlder  clay  overlying  the  Joliet  conglomerate. 

Mt.  Forest  island. — At  Willow  Springs  or  Mt.  Forest.  Strong  "knob- 
and-basin"  topography;  peat  bogs  in  basins. 

Lochport. — East  of  village,  on  upland.  Swell-and-sag  topography; 
moraine  trenched  here  and  there  by  ravines,  near  the  Des  Plaines  valley. 

OLD  SHORELINES   OF   LAKE   CHICAGO. 

Oak  Park. — Hooked  spit,  •  built  at  mouth  of  Des  Plaines  bay  in  the 
Glenwood  stage,     (pp.  69-73;  Fig.  17.) 

Berwyn. — Calumet  beach  is  well  shown  where  La  Grange  interurban 
trolley  car  crosses  it,  near  Oak  Park  avenue.  Flat  lake  plain;  bea(;h 
ridge ;  highway,  line  of  old  oak  trees,  and  old  farm  houses  on  the  beach. 

Riverside. — Calumet  beach  ridge;  deflection  of  the  Des  Plaines  river; 
the  beach  is  not  so  well  shown  here  as  at  Berwyn. 

Summit. — Double-crested  barrier  beach  of  the  Calumet  stage,  along 
Archer  avenue,  east  of  the  village ;  flat  lake  plain  on  the  north ;  floor  of 
old  lagoon  on  the  south ;  stratified  beach  gravels  shown  in  pit  in  north- 
east part  of  village;  hool?ed  end  of  the  barrier  in  southeast  part  of  vil- 
lage, near  school  house ;  middle  portions  of  hooks  cut  off  in  west  part  jf 
village;  Toleston  beach  in  northeast  part,  at  base  of  slope  of  Calum'it 
beach;  turns  into  a  cut  bluff  in  west  of  village,  where  outlet  begins, 
and  continues  thus  to  Mt.  Forest  island,     (pp.  76-80;  Fig.  19.) 

CHICAGO  OUTLET. 

A  very  good  general  view  of  this  may  be  had  on  the  interurban  trolley 
car  that  runs  from  Chicago  to  Joliet. 


9f)  THE   DER   PLAINES   VALLEY. 


Lbull.'/no.  11 


Summit. — Entrance  to  the  outlet  during  the  Calumet  and  TolestoJi 
stage  on  the  west  side  of  Archer  road.     (pp.  74-80;  Fig.  19;  PL  8h.) 

Willow  Springs. — Just  beyond  entrance  to  outlet  at  Glenwood  stage. 
Outlet  cut  deeply  in  moraine;  step  bluff  on  both  sides;  canals. 

Sag  Bridge. — The  "sag,"  the  more  easterly  of  the  two  entrances  of  the 
old  outlet. 

Lemont. — Eock  exposed  in  bluffs  on  both  sides,  and  on  floor ;  at  quar- 
ries on  north  side  of  valley,  striaj  may  be  seen  on  the  floor  of  the  outlet ; 
west  of  village,  qliarries  cut  far  back  into  the  bluffs,  exposing  a  thick 
section  of  the  moraine  and  underlying  glaciated  rock. 

Lochport. —  («)  At  village,  rock  terrace,  remnant  of  sill;  locks  on  old 
canal ;  controlling  works  and  power  plant. 

{b)  On  west  side  of  valley,  opposite  village.  High  terrace  of  gravels, 
remnant  of  outwash  deposit  which  formerly  filled  whole  valley  and  con- 
trolled level  of  Glenwood  stage  of  the  lake ;  gravels  partly  cemented  with 
lime  carbonate,     (p.  51;  Fig.  9;  PI.  3,  No.  3.) 

Jolict. — Flathead  mound,  4  miles  west  of  the  city.  Eemnant  of  out- 
wash  deposit  or  valley  train,  like  that  at  Lockport,  but  in  the  middle  of 
the  valley,     (pp.  51,  52.) 

BED  ROCK  STRUCTURE. 

There  are  many  quarries  in  the  Niagara  limestone,  in  the  Des  Plaines 
valley,  near  Summit,  Lyons,  Lemont,  Eomeo,  Lockport,  and  Joliet. 
At  all  of  these,  features  of  structure  such  as  stratification,  variation  in 
composition  (including  cherty  layers),  jointing,  and  inclined  or  even 
folded  stratification  may  be  seen.  The  following  quarries,  however, 
exhibit  features  of  special  interest: 

Elmliurst. — Quarry  a  mile  west  of  the  station,  on  the  north  side  of  the 
Northwestern  railway.  Joint  cracks  and  fissures  containing  fossilifcr- 
ous  clays  of  Devonian  age.     (pp.  17,  18.) 

Lyons. — Fred  Schultz's  quarry,  in  west  part  of  village.  Devonian 
sediments  in  fissures,  as  at  Elmliurst;  peculiar  folds  in  the  limestone. 

Lockport. — Ravine  at  Dellwood  park.  On  the  walls  of  the  gorge 
gentle  folds  in  the  limestone  are  clearly  shown. 

Joliet. —  (a)  .Gorge  of  Sugar  creel-.  Dislocation  along  a  fault  is 
shown  on  the  southeast  wall,  near  the  slaughter  house  road.  (pp.  21, 
22;  PL  2  B.) 

(&)  Abandoned  pits  and  quarries  in  the  Cincinnati  formation,  afford- 
ing many  fossils,  may  be  found  close  to  the  north  bank  of  the  old 
Illinois-Michigan  canal,  four  miles  west  of  the  city,  and  at  the  west  end 
of  Flathead  mound,  further  down  the  valley,     (p.  14.) 


07 


STATE  GEOLOGICAL  SUEVEY. 

C.  S.  Deneen^  E.  J.  James^  T.  C.  Chamberlin^  Commissioners. 
F.  W.  DeWolf^  Acting  Director. 


LIST  OF  PUBLICATIONS. 

A  portion  of  each  edition  of  the  Bulletins  of  the  State  Geological 
Sui-vey  is  set  aside  for  gratuitous  distribution.  To  meet  the  wants  of 
libraries  and  individuals  not  reached  in  this  first  distribution,  500  copies 
are  in  each  case  reserved  for  sale  at  cost,  including  postage.  'The  reports 
may  be  obtained  upon  application  to  the  State  Geological  Survey,  Ur- 
bana,  Illinois,  and  checks  and  money  orders  should  be  made  payable  to 
F.  W.  DeWolf,  Urbana. 


LIST  OF  PUBLICATIONS. 

Bulletins. 

Bulletin  1.  The  Geological  Map  of  Illinois,  by  Stuart  Weller.  In- 
cluding a  folded,  colored  geological  map  of  the  State  on  the  scale  of  13 
miles  to  the  inch,  with  descriptive  text  of  26  pages.     (Out  of  print.) 

Bulletin  2.  The  Petroleum  Industry  of  Southeastern  Tllinois,  by  W. 
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Bulletin  3.  Composition  and  Character  of  Illinois  Co(ds,  by  S.- W. 
Parr;  with  chapters  on  the  Distrihution  of  the  Coal  Beds  of  the  State, 
by  A.  Bement,  and  Tests  of  Illinois  Coals  under  Steam  Boilers,  by  L.  P. 
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stones for  fertilizers,  on  silica  deposits,  on  coal,  and  on  regions  near  Eas^ 
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.— 7  G  •  . 


98 

BidlctinM.  The  Geoluyical  Map  of  Illinois,  by  Sluurt  Weller.  Second 
edition.  Includes  a  folded  colored  geological  map  of  the  State  on  the 
scale  of  12  miles  to  the  inch,  with  descriptive  text  of  32  pages.  It  in- 
cludes con-ections  and  additions  to  the  former  map  and  text  and  shows 
locations  of  mines  where  coal,  lead,  zinc  and  flourspar  are  produced.  The 
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Bulletin  7.  Physical  Geography  of  the  Evanston-Waul-egan  Region, 
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Separates. 

From  Bidletin  8. 

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Springfield,  by  J.  Claude  Jones;  Bed  Bool-  near  Wheaton,  by  Arthur  C 
Trowbridge;  Middle  Portion  of  the  Illinois  Valley.  l>y  Harlan  PI.  Bar- 
rows.   12  pages,  1  plate,  4  figures.    Postage  2  cents. 

8c.  A  riesian  Wells  in  Peoria  and  Vicinity,  by  J.  A.  Udden.  20  pages, 
1  plate,  1  figure.  Postage  2  cents. 


99 

8d.  Cement  Making  Materials  in  the  Vicinity  of  LaSalle,  by  Gilbert 
H.  Cady;  together  with.  Concrete  Materials  produced  in  the  Chicago 
District,  by  Ernest  F.  Burchard,  a  reprint  from  U.  S.  Geological  Survey, 
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Se.  Contributions  to  the  Study  of  Coal:  Introduction  by  H.  Foster 
Bain;  An  Initial  Coal  Suhsiancc  Having  a  Constant  Thermal  Value,  by 
S.  W.  Parr  and  W.  F.  Wheeler;  Alterations  of  the  Composition  of  Coal 
duHng  Ordinary  Laboratory  Storage,  by  S.  W.  Parr  and  W.  F.  Wheeler; 
Artificial  Modification  of  the  Composition  of  Coal,  by  S.  W.  Parr  and  C. 
K.  Francis;  Weaihering  of  Coal,  by  S.  W.  Parr  and  N.  D.  Hamilton; 
Ash  in  Coal  and  its  Influence  on  the  Value  of  Fuel,  by  A.  Bement;  Coal 
Investigations  in  Saline  and  Williamson  Counties,  Illinois,  and  Coal  In- 
vestigations in  the  Saline-Gallatin  Field,  Illinois,  and  Adjoini^ig  Area, 
by  Frank.  W.  DeWolf;  Notes  on  the  Belleville-Breese  Area,  by  J.  A. 
Udden  and  Frank  W.  DeWolf;  Defects  in  Coal  No.  5  at  Peoria,  by  J.  A. 
JJdden;  Report  on  Field  Worlc  done  in  1907,  by  David  White.  122  pages, 
14  plates,  25  figures. 

8.f.  Clay  Industries  of  Illinois,  Statistics  and  Directory,  by  Edwin 
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Postage  2  cents. 

8h.  Mineral  Industry  of  Illinois,  by  H.  Foster  Bain.  2  pages.  Post- 
age 1  cent. 

8i.  Petroleum  Fields  of  Illinois  in  1907,  by  H.  Foster  Bain.  39 
pages,  1  plate. 

8j.  Stratigraphy  of  Illinois,  Contnbutions  to:  The  Salem  Lime- 
stone, by  Stuart  Weller;  Ljowcr  Paleozoic  Stratigraphy  of  Southivestern 
Illinois,  by  T.  E.  Savage ;  Notes  on  Shoal  Creek  Limestone,  by  Jon  Ud- 
den.   45  pages,  2  plates.    Postage  2  cents. 

8k.     Stream  Improvement  and  Land  Reclamation  in  Illinois,  by  H. 
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From  Bidletin  9. 

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9b.  Qualities  of  High  Grade  Paving  Brick  and  Tests  Used  in  De- 
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9c.  Qualities  of  Clays  Suitable  for  Making  Paving  Brick;  Physical 
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5  cents. 

9d.  Clays  Tested  Which  arc  Suitable  for  Use  in  the  Manufacture  of 
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ments, by  Ira  0.  Baker.     25  pages.     Postage>^  cents. 


100 


Circulars. 


Circular  No.  1.  The  Mineral  Production  of  Illinois  in  1905.  Pam- 
phlet, 14  pages,  postage  2  cents. 

Circular  No.  2.  The  Mineral  Production  of  Illinois  in  1900.  Pam- 
phlet, 16  pages,- postage  2  cents. 

Circular  No.  8.  Statistics  of  Illinois  Oil  Production,  1907.  Folder, 
2  pages,  postage  1  cent. 

Circular  No.  J/..  The  Mineral  Production  of  Illinois  in  1907.  Pam- 
phlet, 16  pages,  postage  2  cents. 


LIBRARY  CATALOGUE  SLIPS. 


[Mount  each  slip  upon  a  separate  cai-d,  placing  the  subject  at  the  top  of  the  second 
slip.  The  name  of  the  series  should  not  be  repeated  on  the  series  card,  but  the 
additional  numbers  should  be  added,  as  received,  to  the  first  entry.] 

Author. 

James  Walter  Goldthwait. — Physical  Features  of  the  Des  Plaino^^ 
Valley.    TJrbana,  University  of  Illinois,  1909. 

(103  pp.  9  pi.)    State  Geological  Survey.    Bulletin  No.  11. 

Subject. 

James  Walter  Goldthwait. — Physical  Features  of  the  Des  Plaines 
Valley.     Urbana,  University  of  Illinois,  1909. 

(103  pp.  21  fig.  9  pi.)    State  Geological  Survey.    Bulletin  No.  II. 

Series. 

State  Geological  Survey.    Bulletin,  No.  11. 

James  W.-vlter  (Joldthwait. — Physical  Features  of  the  Des  Plaines 
Valley. 


101 


INDEX. 


Page. 

Alluvial  fans  and  cones 64 

Berwyn,  beach  at 95 

Blue  Island,  beach  at 77 

Calumet  stage  of  Lake  Chicago  54,74 

Cambrian  period,  description  of 11 

Cones,  alluvial 64 

Caves,  description  of 25 

Cincinnati  formation,  at  Lockport 10 

Quarries 96 

Chicago  outlet,  abandonment  of < 56 

Chicago  pass 1 

Conglomerate,  Joliet 42 

Cooley,  L.  E.,  quoted 6,7,8,88 

Dell  wood  Park,  ravine 96 

Des  Plaines  basin,  description  of 3 

Des  Plaines  river,  a  young  stream 86 

Description  of 4 

Floodsof .'  88 

Geography  and  history  of 1 

Lower,  history  and  description  of 46 

Upper 66 

Devonian  period,  description  of 17 

Drift,  complexity  of 35 

Distribution  and  surface  form  of 33 

Stratified 38 

Thickness  of 34 

Driftless  area,  description  of 24 

Elmhurst,  fossils  at 17 

Moraine  at j. 95 

Quarry  at 96 

Erosion  by  tributary  streams 57 

Examples  of 94 

Explorations  of  Louis  Joliet 1 

Fans,  alluvial 64 

Faults  in  rock 21 

Floods  on  the  Des  Plaines S8,92 

Folds  in  rock • 19 

Fraction  run , 57 

Fullersburg,  salt  creek  at 67 

Glacial  and  Inter-Glacial  deposits 33 

Glaciation,  discussion  of 26 

Glen  wood  stage  of  Lake  Chicago 52,67 

Harlem,  erosion  near 83,94 

Hawthorne,  beach  at 79 

Hickory  Creek ■ 59,95 

Hinsdale,  Moraine  at 95 

History  of  Des  Plaines  river 1 


103 

Index —  Continued . 

Page. 

Igneous  rocks •       37 

Illinois  glacial  epoch .' 27 

Illinois- Michigan  canal 1,5,8 

Joints  in  rock 20  ' 

Joliet,  conglomerate '  42 

Fault  near 21 

Floods  near t)2 

Louis,  explorations  of 1 

Moraine  at g.j 

Outlet  at : % 

Phenomena  at 95 

Terrace  at 51 

Kellar's  gravel  pit '. 42 

La  Grange,  shore  line  at 73 

Lake  Chicago 67 

Calumet  stage 54,74 

Excavation  by  outlet 52 

Features  of 4 

(jlen wood  stage 52, 67 

Shore  lines  of 95 

Toleston  stages 55, 78 

Lake  Michigan,  formation  of 81 

Lemont,  outlet  at 96 

Leverett,  Frank,  quoted 32 

Lockport,  Moraine  at 95 

Outlet  at J 96 

Quarry  at. "  96 

Sill  at ■. 54 

Terrace  at ; 51 

Long  run 59 

Lower  Magnesian  limestone  at  Lockport '. 10 

Lyons,  fossils  at 17,18 

Quarry  at 96 

Madison  street  bridge,  phenomena  at 87 

Maywood,  phenomena  at 94 

Maywood,  shore  line  at 73 

McCook,  shore  line  at 74 

Meanders,  origin  of 54 

Metamorphic  rocks 38 

Minooka  till  ridge 3,48 

Moraine,  at  Elmhurst 95 

At  Hindsdale 95 

At  Joliet ; 95 

At  Lockport 95 

At  Mt.  Forest  Island 95 

Near  Oak  Park 5 

Valparaiso *9-52 

Wisconsin *" 

Morris  Basin,  lake  in ^^ 

Mt.  Forest  Island  moraine 52 

Mt.  Forest,  shore  line  at 73, 78 

MuQ  Lake 5,6 

Niagara  limestone,  at  Lockport 10 

Description  of 14, 15 

Oak  Park,  beaches  at 95 

Moraines  near • * 

Spit  at ^9 

Ogden  dam 5 

Ordovician  period,  description  of 12 


103 

Index — Concluded. 

Page. 

Outwash  from  Valparaiso  moraine 49 

Overliolser's  graver  pit .■ .'  40 

Peneplain  in  northern  Illinois 24 

Potsdam  sandstone  at  Lockport iO 

Pre-Glacial  topography 25 

Reed's  woods 60 

River  development 84 

River  erosion^  examples  of 94 

Riverside,  beaches  at 76,95 

Phenomena  at 94 

Rocks,  Igneous 37 

Metamorphic , 38 

Sedimentary 37 

St.  Peters  sandstoiiC  at  Lockport 10 

Sag  bridge,  outlet  at. 96 

Sanitary  District  of  Chicago 8 

Sedimentary  rocks 37 

Silurian  period,  description  of 14 

Spit  at  Oak  Park 69 

Spring  Creek 59 

Stratified  drift .' 38 

Summit,  beaches  at 95 

Sugar  Creek 60 

Gorge  of .96 

Phenomena  of 95 

Till,  description  of —  36 

Toleston  stages  of  Lake  Chicago .55,78 

Topography,  Pre-glacial 25,31 

Trenton  limestone  at  Lockport 10 

Valparaiso  moraine,  its  outwash 49 

Position  of 3 

Weller,  Stuart,  quoted 17 

Willow  Springs,  outlet  at « 96 

Wisconsin  drift,  early  deposition  of - 47 

Late  deposition  of 48 


V', 


I 


